POWER QUALITY SOLUTIONS

Switchgear Factory, Navi Mumbai

ABOUT US
Larsen & Toubro is a technology-driven company that infuses
engineering with imagination. The Company offers a wide
range of advanced solutions in the field of Engineering,
Construction, Electrical & Automation, Machinery and
Information Technology.

L&T Switchgear, a part of the Electrical & Automation

business, is India's largest manufacturer of low voltage
switchgear, with the scale, sophistication and range to meet
global benchmarks. With over five decades of experience in
this field, the Company today enjoys a leadership position in
the Indian market with a growing international presence.

It offers a complete range of products including powergear,

controlgear, industrial automation, building electricals &
automation, Power Quality Solutions, energy meters, and
protective relays. These products conform to Indian and
International Standards.
Switchgear Factory, Ahmednagar

Switchgear Factory, Vadodara

 Page No.

CONTENTS
Products of Power Quality
Power Factor Correction
Benefits of Using LT Capacitors over HT Capacitors
¶
¶
Capacitor Technology
¶
Life of Power Capacitors
¶
Capacitor Power Loss Calculation
¶
Discharge Resistors
1
4
5
7
9
10
11
¶
Voltage Selection of Power Capacitors 12
Standard Duty Capacitors
¶ 13
Heavy Duty Capacitors
¶ 15
Super Heavy Duty Capacitors
¶ 18
LTXL: Ultra Heavy Duty Capacitors
¶ 20
Harmonics 26
¶
Harmonic Amplification 27
¶
Harmonic Resonance 28
¶
Interpretation of Total Harmonic Distortion (THD) 30
¶
Understanding Current & Voltage Harmonics 31
¶
Triplen Harmonic Mitigation 35
¶
Harmonic Mitigation 37
¶
Detuned Filters 38
¶
Importance of Using The Right Detuned Reactor 40
¶
Linearity of Reactor 42
¶
Q-factor 43
¶
Reactors - Harmonic Filters 44
¶
Basics of Active Harmonic Filters 47
¶
Active Harmonic Filters 51
Harmonics and its Impacts on Power Factor
¶ 55
Capacitor Switching in APFC Panel 58
¶
Capacitor Duty Contactors – Type MO C 59
¶
Dynamic Power Factor Correction 64
¶
Thyristor Switching Modules 68
etaCON - APFC Controller 72
Selection of Capacitor 80
¶ Motor Power Factor Compensation 84
¶ Transformer Compensation 86
¶ Reactive Power Compensation of DG Sets 87
etaSYS - Standard APFC Panels 89
¶ Capacitor Step Size Selection Guidelines in APFC Panels 96
¶
Fuse Selection for APFC Panels 99
¶
MCCB Selection for APFC Panels 100
¶
Cable Selection for Capacitors 101
¶
Thermal Design of APFC Panels 102
etaPRO V2.3 - Multi-utility Software Package 106
1 PRODUCTS OF POWER QUALITY

POWER
CAPACITORS

Cylindrical Box
Type Type

Standard Duty Heavy Duty Super Heavy LTXL: Ultra Standard Duty Heavy Duty LTXL: Ultra
1-25 kVAr 1-30 kVAr Duty Heavy Duty 1-30 kVAr 1-50 kVAr Heavy Duty
3-33 kVAr 5-25 kVAr 5-50 kVAr

HARMONIC
FILTERING

Detuned Harmonic Filter Active Harmonic Filter

5-100 kVAr 30-600A
Copper and Aluminium 3Ph 3Wire/4 Wire
7% and 14%
 2

CAPACITOR
SWITCHING

Thyristor Switching Modules Capacitor Duty Contactors -

10, 25 & 50 kVAr Type MO C
3-100 kVAr

POWER
FACTOR
CONTROLLER

etaCON M Series APFC Controller

Upto 14 steps

REACTIVE
POWER
MANAGEMENT
SOLUTIONS

etaSYS APFC Panels

35 - 500 kVAr
 POWER FACTOR CORRECTION 4
Principles of Power Factor Correction
A vast majority of electrical loads in low voltage industrial installations are inductive in nature. Typical examples are
motors and transformers, which consume both active and reactive power. The active power is used by the load to
meet its actual work requirements whereas reactive power is used by the load to meet its magnetic field
requirements. The reactive power (inductive) is always 900 lagging with respect to active power as shown in figure1.
Figure 2 & 3 show the flow of kW, kVAr and kVA in a network.

Supply Bus Supply Bus

Active Power
kVA kVA
kVAr

kW kVAr kW
Reactive
Power
LOAD LOAD
Capacitor

Figure 1: Figure 2: Figure 3:

Phase relationship Network without Capacitor Network with Capacitor
between Active and
Reactive Power

Flow of active and reactive power always takes place in electrical installations. This means that the supply system has
to be capable of supplying both active and reactive power. The supply of reactive power from the system results in
reduced efficiency of the installation due to:
Increased current flow for a given load
n

Higher voltage drops in the system

n

Increase in losses of transformers, switchgear and cables

n
Higher kVA demand from supply system as given in figure 2
n
Higher electricity cost due to levy of penalties / loss of incentives
n

It is therefore necessary to reduce & manage the flow of reactive power to achieve higher efficiency of the electrical
system and reduction in cost of electricity consumed.
The most cost effective method of reducing and managing reactive power is power factor improvement through
Power Capacitors. The concept of reduction in kVA demand from the system is shown in figure 3.

Benefits of Power Factor Correction

Reduction in
line current
n Reduction in
Reduction in power loss
kVA demand n Reduction in
Reduction in nReduction in
kVAr demand cable size
Power factor transformer n Reduction in
correction rating switchgear
rating

Cost benefits No penalties

n Reduced
n electrical Reduced
n energy
Incentive
n equipment cost charges
Reduction
n in kVAh
units consumed
 BENEFITS OF USING LT CAPACITORS OVER
5 HT CAPACITORS
Power factor compensation can be provided on either LT or HT side of the distribution transformer for the loads at LT
side. Often compensation is done on the HT side as the electricity board measures power factor on HT side for penalty
calculation. Also, HT capacitors involve low initial investment as compared to LT capacitors. However, compensation
achieved by HT capacitors does not provide the benefits offered by the use of LT capacitors, as discussed in this
article.
Consider two cases with compensation provided on HT and LT side respectively as shown in figure 1 and 2.

Supply Supply

kVAr

kW kW
kVAr

Distribution HT Capacitor Distribution

Transformer Transformer

kVAr
CB CB
kW kVAr kW

LT Capacitor

LT Load LT Load

Fig 1: Compensation on HT Side Fig 2: Compensation on LT Side

As seen in fig 1, with the capacitor connected on the HT side, the compensated reactive power flow through the
transformer does not reduce and hence there is no change in current flow. Although the HT side power factor is
improved, the LT side power factor remains same. However, as seen in fig 2, connecting capacitor on LT side reduces
the reactive power flow through the transformer and we get improved power factor and reduced current flow on
both LT and HT sides.

1. Reduction in Transformer Copper Losses

Consider a load of 1200 kW connected to a transformer of 2000 kVA. The typical full-load copper losses in a 2000
kVA transformer are 25000 W.
When compensation is provided on HT side, operating power factor of the transformer is 0.75 (same as
uncompensated), denoted by cosø1.
When compensation is provided on LT side, operating power factor of the transformer is 0.98 (compensated),
denoted by cosø2.
 6

Power Saving (in W) = 25000*0.6*(1/.75-1/.98) = 4694 W

Monthly Energy Savings (in kWh) = 4694 *24*30/1000 = 3380 kWh
Typical Energy Charge (in Rs / kWh) = Rs. 6 per kWh
Monthly Cost Saving (in Rs) = 6*3380 = Rs. 20278/-
Yearly Cost Savings (in Rs) = 20278*12 = Rs. 243330/-

Thus, LT compensation provides monthly savings of Rs. 20,278/- for a 2000 kVA transformer. Additionally, the
operating temperature of the transformer is relatively less because of reduced copper losses. Hence, apart from
monetary benefits, LT compensation also ensures longer life of the transformer.

2. Capacity Release in Transformer

Consider a 2000 kVA transformer connected to a load.

Cast 1: When compensation is provided on HT side, operating PF of transformer = 0.75

Maximum load that can be connected = 2000*0.75 = 1500 kW

Cast 2: When compensation is provided on LT side, operating PF of transformer = 0.98

Maximum Load that can be connected = 2000*0.98 = 1960 kW
Additional load that can be connected under the same transformer = 460 kW

LT compensation allows release of capacity of 460 kW with the same transformer. Thus, additional load can be easily
connected to the system without any additional investments in new transformers.

3. Optimized Main Incomer Switchgear Rating

LT side capacitor, when connected after the main incomer reduces the current drawn by the same set of loads. Hence
incomer switchgear rating can be optimized and the investment cost of the main incomer can be reduced.

Apart from those mentioned above, LT compensation also offers other advantages, such as
• Maintenance of LT capacitors and panels is easier and does not require complex safety measures
• Spares and accessories for the same are easily available and relatively cheaper
Thus, for a factory with all LT loads, power factor compensation with LT capacitors proves to be a better option, with
its relatively smaller payback period.
7 CAPACITOR TECHNOLOGY
MPP (Metalized Poly-propylene)
Capacitors are used in diverse applications, and hence different capacitor technologies are available. In low voltage
applications, LT cylindrical capacitors which are made in accordance with metalized polypropylene technology, have
proved to be the most appropriate and the most cost effective amongst all technologies. Depending on the nominal
voltage of the capacitor, the thickness of the polypropylene film differs.

Electrodes (metalized)

Poly-propylene Film

Electric Contact
Ž

Non-metalized Edge
Design of LT Capacitor

Self - Healing
At the end of service life, or due to inadmissible electrical or thermal overload, an insulation breakdown may occur.
This breakdown causes a small arc which evaporates the metal layer around the point of breakdown and hence re-
establishes the insulation at the place of perforation. After electric breakdown, the capacitor can still be used. The
decrease of capacitance caused by a self-healing process is less than 100 pF. The self-healing process lasts for a few
microseconds only and the energy necessary for healing can be measured only by means of sensitive instruments.

Polypropylene Film Electrodes (metalized)

Point of Breakdown

Top View
Non-conductive Insulating Area

Self - Healing Breakdown

Impregnation
Our LT-type capacitors are impregnated to safeguard from environmental influences and to guarantee reliable, long-
term operation. Vacuum impregnation eliminates air and moisture, improves “self-healing” and reduces thermal
resistance.
 8
Over Pressure Disconnector (OPD)
At the end of service life or after several self-healing operations or due to inadmissible electrical or thermal overload,
over pressure builds up and causes an expansion of the cover. Expansion over a certain limit causes the tear-off of the
internal fuses. The active capacitor elements are thus cut-off from the source of supply. The pressure within the
casing separates the breaking point so rapidly that no harmful arc occurs.

Operating Condition

Torn - off Condition

Construction Details
Cylindrical capacitors consist of three units of single phase capacitors connected in delta kept inside an aluminium
can. Technologically similar to cylindrical capacitors, box type capacitors consist of three or six single phase
cylindrical capacitor cells. The individual cells are wired together and mounted on a steel frame. The steel frame
together with the cells is housed in a common sheet steel casing. The enclosure is powder coated and is designed to
protect the capacitor cells from dust and moisture. Ease of mounting is ensured by 4 drillings at the bottom of the
container.
This design ensures highest safety by:
n Self healing technology
n Over pressure tear - off fuse
n Robust steel container
n Massive connection studs

MPP Capacitors are manufactured in three different types - Standard duty, Heavy duty and Super heavy duty. The
Standard duty capacitors are manufactured using standard thickness of dielectric material with heavy edge
metalization. Heavy duty and Super heavy duty capacitors are manufactured using thicker material and in lower
width which increases current handling capacity as well as reduces temperature rise.
9 LIFE OF POWER CAPACITORS
The life of a capacitor is influenced by the following three parameters:
• Temperature
• Voltage
• Current

Temperature
For a capacitor, the temperature depends upon the following parameters:
n Ambient temperature at which capacitor is being operated
n Amount of over current that flows through the capacitor
n Power loss of the capacitor (dielectric power loss and resistive power loss)
The increase in temperature results in faster degradation of the dielectric. For every 10°C rise in temperature, the life
of the capacitor is halved. Faster the degradation of the dielectric, lower will be the life of the capacitor.
Increase in temperature beyond a certain limit may result in expansion of impregnation and dielectric material. This
may result in bulging of capacitors. In worst case, capacitor may even burst, if it does not have an over-pressure
disconnector.
The capacitor must thus be operated at rated ambient temperature for a long operating life.
Capacitors are classified in temperature categories, each category being specified by a number followed by a letter.
The number represents the lowest ambient air temperature at which the capacitor may operate. The letters represent
upper limits of temperature variation ranges.
Letter symbols for upper limit of temperature range as per IEC 60831 are as follows :

Ambient Temperature
Symbol Highest mean over any period of
Maximum
24 h 1 year
A 40 30 20
B 45 35 25
C 50 40 30
D 55 45 35

Voltage
The increase in system voltage has the following effects on the capacitor:
Dielectric degradation
n

If the voltage increases beyond a certain limit, the dielectric material will breakdown. This critical voltage is called
the dielectric breakdown voltage. Breakdown can result in an internal short circuit causing the capacitor to fail
permanently.
Increase in current flow through the capacitor
n

As capacitors are linear in nature, with increase in voltage, the capacitor current also increases because XC remains
constant (IC =V/XC). This results in overloading of the capacitor, which may reduce the life of the capacitor. Over
voltage limits of the capacitors are +10% for 8 hrs in 24 hrs, +15% for 30 min in 24h, +20% for 5 min in 24 hrs
and +30% for 1 min in 24 hrs.

Current
The parameters that are related to current, which affect the life of the capacitor are:
Inrush current
n

Whenever the capacitor is switched on, it draws a huge inrush current which goes up to levels even greater than
100 times the capacitor rated current. Frequent switching of the capacitor without proper inrush current limiting
devices will affect the life of the capacitor as it is heavily stressed during each switching operation. Switching
frequency and amplitude of inrush current thus influences the life of the capacitor.
Over-load current
n

Continuous overload of capacitor is mainly because of harmonics and continuous over voltage. Overloading
results in local hot spots and may lead to an internal short circuit.

To conclude, all the above parameters should be within the rated value in order to exploit the maximum life of the
capacitor.
 CAPACITOR POWER LOSS CALCULATION 10
A capacitor is a passive device which has two conductors separated by a dielectric of infinite resistance, ideally.
Hence, it should offer only capacitive reactance, with zero resistance and zero inductance values. But practically, the
dielectric of the capacitor will offer a finite resistance along with the capacitance. This finite resistance is called as
Equivalent Series Resistance (ESR), and its equivalent circuit can be represented as below:

The ESR in the capacitor causes the leakage current to flow through the dielectric of the capacitor. This results in real
power loss (I 2 *ESR) called as dielectric loss. Higher the ESR, higher is the power loss, and hence the heat generated by
the capacitor is also more. The heat generated should be dissipated properly; otherwise it may result in significant
temperature rise. A good quality capacitor has very low ESR value.
In a lossless (ideal) capacitor, the current leads the voltage exactly by 90°. But there is always a small shortfall in the
lead angle from 90°, because of the dielectric loss. The difference in angle is called loss angle (d ). The following
diagram represents loss angle (d ) in the impedance plane.
The tangent of the loss angle (loss tangent) is defined as the ratio of the capacitor's equivalent series resistance (ESR)
to the capacitive reactance (XC ).

Impedance plane

ESR

-jXC

Where, Q is the reactive power rating of the capacitor (in VAr).

Typically, for good quality power capacitors, tan d value is less than 0.0002. Power loss of any capacitor can be
computed if tan d value is known as explained in the example below:
For a 10 kVAr capacitor, consider the value of tan d
as 0.0002.

Normally, the tan d

value is available in the routine test certificate of the power capacitor.
The life of a power capacitor is largely dependent upon temperature. Hence, it is a good practice to do the thermal
design of APFC panel after computing the capacitor power loss.
11 DISCHARGE RESISTORS
Typically, power factor correction capacitors are fitted with discharge resistors
connected directly across the terminals (two resistors between three phases).
These resistors are mandatory safety requirement recommended by the capacitor
standards, to discharge the residual voltage that remains in the capacitor, once it
is switched off.
As per IEC 60831 (MPP capacitors) and IEC 60931 (APP capacitors) the capacitor
should discharge to 75 V or below within 3 min as soon as the capacitor is
switched off. This is to protect human beings from the risk of electric shock and Cylindrical capacitor's
also for safe re-switching of the same capacitor in APFC panel. As a general terminal block
practice, discharge resistors bring the voltage to below 50 V in 1 min, which is with discharge resistor
safer.

If the capacitor is re-switched without discharging

sufficiently, there is a possibility that the voltage
difference across the contactor may shoot up to 1000 V.
More over, this results in very high peak inrush current as
the rate of change of voltage is very high (IC = C dV/dt).
Such frequent switchings reduce the life of the capacitor
and/or the contactor, and may cause premature failures.
Hence while re-switching the capacitor (either in manual
mode or auto mode) it is mandatory to discharge the
capacitor to its 10% rated voltage.

In order to ensure the sufficient discharge, it should be ensured that the capacitor is re-switched only after 45 to 60
seconds. This time delay (for re-switching the same capacitor bank) can be set in APFC relay. In case, any application
demands frequent switching of capacitors by contactors, time delay can be reduced by faster discharge of the
residual voltage. Faster discharging can be achieved by replacing the existing resistors with new resistors of lesser
resistance.

Formula to calculate the resistance is:

2Vn

The above formula is valid for resistors assembly in the delta connected capacitor (two resistors between three
terminals), as shown in the figure.

However, opting for lower resistance for faster discharge will increase the
power loss. At the same time, appropriate power rating (wattage) of the
resistor should be chosen to ensure sufficient current carrying capacity of R R
the resistor.

Here, the resistor should withstand the initial peak discharge current even if the capacitor is switched off at the
instant of 30% over voltage.
 VOLTAGE SELECTION OF POWER CAPACITORS 12
The name plate of a capacitor usually has three kVAr ratings
at three different voltages. kVAr rating of the capacitor is
directly proportional to square of the applied voltage.
This is evident from the below formula:

V2
kVAr =
XC
As capacitance (C in uF) remains same for a capacitor,
XC will remain constant.

For example, if a capacitor is rated for 30 kVAr at 480 V,

and if the applied voltage is 440 V, the kVAr output can be
calculated as follows:

(Applied voltage)2
kVAr output = Rated kVAr x 2
(Rated voltage)
2
(440)
= 30 x
(480)2
= 25.2 kVAr at 440 V
Capacitor label

Similarly, if we apply 500 V for the same capacitor, the kVAr output will be 32.5 kVAr. In this case, we are applying
voltage more than the rated value and the capacitor will deliver kVAr output more than its rated value. Hence the life of
the capacitor may reduce drastically, because of over-voltage and over-current.

To summarize, the product label of a capacitor (for e.g. 30 kVAr, 480 V) has the following details as shown above.

Similarly, for 25 kVAr and 440 V capacitor, the name plate contains the respective kVAr ratings and current ratings at
440 V, 415 V and 400 V.

Selection of Capacitors When System Voltage is 415 V

Before deciding the voltage of the capacitor, it is important to understand the percentage impedance of the
transformer (% Z). The percentage impedance is the voltage drop on full load due to the winding resistance and
leakage reactance of the transformer. This is expressed as a percentage of the rated voltage. For example, if the
secondary of the transformer is rated for 433 V and %Z is 4%, the voltage available at the load end, during full load
conditions, would be 415 V only. When the load decreases, the voltage drop decreases and hence the voltage at the
load end increases. During no-load conditions, the voltage can reach a maximum of 433 V.
If a capacitor is selected with 415 V (in the above case), it would be subjected to over-voltage during partial load or no-
load conditions. This would impact the capacitor life drastically. For a normal capacitor, following are the over-voltage
limits permitted as per IEC:
• 10% over-voltage for 8 hours in every 24 hours
• 15% over-voltage for 30 minutes in every 24 hours
• 20% over-voltage for 5 minutes in every 24 hours
• 30% over-voltage for 1 minute in every 24 hours

Hence, the capacitor should be rated for 440 V, even though the voltage at the load end is measured as 415 V. In
general, it is a better practice to select capacitor voltage greater than the rated secondary voltage of the transformer
and hence, avoid prolonged over-voltage conditions.
13 STANDARD DUTY CAPACITORS
L&T Standard Duty Capacitors are metalized polypropylene
capacitors from 1 - 25 kVAr in cylindrical configuration and 1-30
kVAr in box type configuration. These capacitors come with a
stacked winding and are impregnated with a biodegradable soft
resin. These capacitors are self healing type. The Capacitors come
with an over pressure disconnector and finger proof terminals.
They can be used to provide effective power factor correction in
industrial and semi industrial applications.
For Selection and Application details please refer page no. 80

Technical Details
Standard Duty
Box Cylindrical
LTBCF (1 to 6 kVAr) and LTCCF (1 to 6 kVAr)
Series
LTBCD (7.5 kVAr and above) LTCCD (7.5 kVAr above)
Range 1 - 30 kVAr 1 - 25 kVAr

IS 13340-2012, IS 13341-1992, IS 13340-2012, IS 13341-1992,

Standards
IEC 60831-1+2 IEC 60831-1+2
Rated Frequency 50 Hz 50 Hz
Rated Voltage 415 / 440 V 415 / 440 V

+10% (8h/24h), +15% (30m/24h), +10% (8h/24h), +15% (30m/24h),

Over Voltage
+20% (5m/24hrs), +30% (1m/24hrs) +20% (5m/24hrs), +30% (1m/24hrs)
Overcurrent 1.5 x In 1.5 x In
Peak Inrush Current 200 x In 200 x In
Operating Losses (Dielectric) < 0.2 W / kVAr < 0.2 W / kVAr
Operating Losses (Total) < 0.45 W / kVAr < 0.45 W / kVAr
Tolerance on Capacitance -5 / +10% as per IS -5 / +10% as per IS
Test Voltage (Terminal-Terminal) 2.15 Times rated voltage for 10 sec 2.15 Times rated voltage for 10 sec
Test Voltage (Terminal-Casing) 3 kV (AC) for 1 minute 3 kV (AC) for 1 minute
Degree of Protection IP20, Indoor mounting (IP54 optional) IP20, Indoor mounting (IP54 optional)
-25 / D -25 / D
Max temperature = +55OC Max temperature = +55OC
Ambient Temperature O O
Max mean temperature (24 h) = +45 C Max mean temperature (24 h) = +45 C
O O
Max mean temperature (1 year) = +35 C Max mean temperature (1 year) = +35 C
Cooling Natural or forced air cooling Natural or forced air cooling
Permissible Relative Humidity Max 95% Max 95%
Maximum Operating Altitude 4000 m above sea level 4000 m above sea level
Mounting Upright Upright
Overpressure disconnector, Self-healing, Overpressure disconnector, Self-healing,
Safety Features
Finger-proof terminals Finger-proof terminals
Impregnation Non-PCB biodegradable resin Non-PCB biodegradable resin
Casing MS Sheet metal Aluminum extruded can
Dielectric Composition Metalized polypropylene Metalized polypropylene
Wire length 150mm (1 - 6 kVAr) Wire length 150mm (1 - 6 kVAr)
Terminals
Ceramic bushing (7.5 kVAr and above) Finger-proof clamptite (7.5 kVAr and above)

Discharge resistors fitted, Discharge resistors fitted,

Discharge Resistors / Time
Standard discharge time 60 seconds Standard discharge time 60 seconds
Switching Operations (maximum) 5000 Switchings per year 5000 Switchings per year
Life* 1,00,000 hrs 1,00,000 hrs

*at standard operating conditions

 14
Standard Duty Capacitors - Overall Dimensions

Cylindrical Type Finger proof terminal

Power rating Dimensions

Sr. Voltage (kVAr) Capacitance Rated current in (mm)
(uF) (A) Cat. Nos.
No.
50 Hz 60 Hz H D

Expansion to h ± 3+a
1 440 V 1 1 16.44 1.31 130 45 LTCCF301B2

h + 40
2 440 V 2 2 32.88 2.62 130 50 LTCCF302B2 Marking

h±3
3 440 V 3 4 49.32 3.94 165 50 LTCCF303B2

4 440 V 4 5 65.77 5.25 165 63.5 LTCCF304B2

d
5 440 V 5 6 82.21 6.56 225 63.5 LTCCF305B2

6 440 V 6 7 98.65 7.87 225 63.5

±1
LTCCF306B2

16
Torque T - 10 Nm
M 12
7 440 V 7.5 9 123.31 9.84 195 75 LTCCD307B2 Toothed locked washer
DIN 6798
8 440 V 8.33 10 136.96 10.93 195 75 LTCCD308B2 Hexagon nut
DIN 934-M 12
Tightening torque
9 440 V 10 12 164.42 13.12 195 85 LTCCD310B2 T= 1.2 Nm

10 440 V 12.5 15 205.52 16.40 270 85 LTCCD312B2

11 440 V 15 18 85

19.6 ± 0.5
246.62 19.68 270 LTCCD315B2
16.8 ± 0.5
12 440 V 20 24 328.83 26.24 345 85 LTCCD320B2
Note :- 1) Seaming adds 4mm. In diameter
13 440 V 25 30 411.04 32.80 345 90 LTCCD325B2

Box Type
7.5 kVAr to 15 kVAr
Power rating Dimensions
Capacitance Rated
2 Slot 8x10
Sr. Voltage (kVAr) current in (mm)
No. (uF) Cat. Nos.
(A)
50 Hz 60 Hz H W D W±5

1 440 V 1 1 16.44 1.31 125 140 40 LTBCF301B2 D±5

2 440 V 2 2 32.88 2.62 125 140 40 LTBCF302B2

3 440 V 3 4 49.32 3.94 145 170 50 LTBCF303B2

H±5

4 440 V 4 5 65.77 5.25 145 170 50 LTBCF304B2

EMBOSSING

5 440 V 5 6 82.21 6.56 175 170 50 LTBCF305B2

6 440 V 6 7 98.65 7.87 175 170 50 LTBCF306B2

7 440 V 7.5 9 123.31 9.84 300 240 80 LTBCD307B2

20 kVAr to 30 kVAr
8 440 V 8.33 10 136.96 10.93 300 240 80 LTBCD308B2 4 Slot 8x15

9 440 V 10 12 164.42 13.12 300 240 80 LTBCD310B2

75 ±1

10 440 V 12.5 15 205.52 16.40 300 240 80 LTBCD312B2

D±5
W±5
11 440 V 15 18 246.62 19.68 300 240 80 LTBCD315B2 Hole Ø30 mm
for cable entry
12 440 V 20 24 328.83 26.24 300 240 160 LTBCD320B2

13 440 V 25 30 411.04 32.80 300 240 160 LTBCD325B2

H±5

14 440 V 30 36 493.25 39.37 300 240 160 LTBCD330B2 EMBOSSING

15 HEAVY DUTY CAPACITORS
L&T Heavy Duty Capacitors are metalized polypropylene capacitors
available from 1-30 kVAr in cylindrical and from 1-50 kVAr in box type
construction. These capacitors have an inrush current withstand of
300 In and an overload withstand capacity of 1.8 In. These capacitors
have all the features of standard capacitors like over pressure
disconnector and self healing.
The cylindrical capacitors are subjected to an extended period of
drying after which the casing is filled with an inert gas to prevent
corrosion of the winding elements and inner electrical contacts.
Compact design ensures space saving. Heavy Duty capacitors have a
long life of 150000 hours.
For Selection and Application details please refer page no. 80

Technical Details
Heavy Duty
Box Cylindrical
LTCCH (1 - 2 kVAr)
Series LTBCH
LTCCN (3 - 30 kVAr)
Range 1 - 50 kVAr 1 - 30 kVAr
IS 13340-1993, IS 13341-1992, IS 13340-1993, IS 13341-1992,
Standards
IEC 60831-1+2 IEC 60831-1+2

Rated Frequency 50 Hz 50 Hz
Rated Voltage 415 / 440 / 480 / 525 V 415 / 440 / 480 / 525 / 690 V
+10% (8h/24h), +15% (30m/24h), +10% (8h/24h), +15% (30m/24h),
Over Voltage
+20% (5m/24hrs), +30% (1m/24hrs) +20% (5m/24hrs), +30% (1m/24hrs)

Overcurrent 1.8 x In 1.8 x In

Peak Inrush Current 300 x In 250 x In
Operating Losses (Dielectric) < 0.2 W / kVAr < 0.2 W / kVAr
Operating Losses (Total) < 0.35 W / kVAr < 0.35 W / kVAr
Tolerance on Capacitance -5 / +10% as per IS -5 / +10% as per IS
Test Voltage (Terminal-Terminal) 2.15 times rated voltage for 10 sec 2.15 times rated voltage for 10 sec
Test Voltage (Terminal-Casing) 3 kV (AC) for 1 minute 3 kV (AC) for 1 minute
Degree of Protection IP20, indoor mounting, (IP54 optional) IP20, indoor mounting, (IP54 optional)
-25 / D -40 / D
O
Max temperature = +55 C Max temperature = +55OC
Ambient Temperature O O
Max mean temperature (24 h) = +45 C Max mean temperature (24 h) = +45 C
O O
Max mean temperature (1 year) = +35 C Max mean temperature (1 year) = +35 C
Cooling Natural or forced air cooling Natural or forced air cooling
Permissible Relative Humidity Max 95% Max 95%
Maximum Operating Altitude 4000 m above sea level 4000 m above sea level
Mounting Upright Upright or horizontal
Overpressure disconnector, Overpressure disconnector,
Safety Features
Finger-proof terminals, Self-healing Finger-proof terminals, Self-healing

Impregnation Non PCB biodegradable resin LTCCH - resin, LTCCN - Inert gas
Casing MS Sheet metal Aluminum extruded can
Dielectric Composition Metalized polypropylene Metalized polypropylene
Terminals Ceramic bushing Finger-proof clamptite
Discharge resistors fitted, Discharge resistors fitted,
Discharge Resistors / Time
Standard discharge time 60 seconds Standard discharge time 60 seconds

Switching Operations (maximum) 8000 Switchings per year 8000 Switchings per year
Life* 1,50,000 hrs 1,50,000 hrs

*at standard operating conditions

 16
Heavy Duty Capacitors - Overall Dimensions

Cylindrical Type

Marking
Impregnating hole
5 ± 0.5

Torque
T = 1.2 Nm
h + 40

19.6 ± 0.5
d
h

16.8 ± 0.5
16 + 1

Torque
M12
T = 10 Nm

Power rating Dimensions

Sr. Voltage (kVAr) Capacitance Rated current in (mm)
No. (uF) (A) Cat. Nos.
50 Hz 60 Hz H D
1 440 V 1 1 16.44 1.31 167 55.5 LTCCH301B2
2 440 V 2 2 32.88 2.62 170 66 LTCCH302B2
3 440 V 3 4 49.32 3.94 130 64 LTCCN303B2
4 440 V 4 5 65.77 5.25 190 64 LTCCN304B2
5 440 V 5 6 82.21 6.56 190 64 LTCCN305B2
6 440 V 7.5 9 123.31 9.84 190 64 LTCCN307B2
7 440 V 8.33 10 136.96 10.93 190 64 LTCCN308B2
8 440 V 10 12 164.42 13.12 265 64 LTCCN310B2
9 440 V 12.5 15 205.52 16.40 265 64 LTCCN312B2
10 440 V 15 18 246.62 19.68 190 84.4 LTCCN315B2
11 440 V 20 24 328.83 26.24 265 84.4 LTCCN320B2
12 440 V 25 30 411.04 32.80 265 84.4 LTCCN325B2
13 480 V 7.5 9 103.62 9.02 190 64 LTCCN307C2
14 480 V 12.5 15 172.69 15.04 190 84 LTCCN312C2
15 480 V 15 18 207.23 18.04 265 84 LTCCN315C2
16 480 V 20 24 276.31 24.06 265 84 LTCCN320C2
17 480 V 25 30 345.39 30.07 265 84 LTCCN325C2
18 480 V 30 36 414.47 36.09 230 116 LTCCN330C2
19 525 V 7.5 9 86.61 8.25 190 64 LTCCN307M2
20 525 V 8.33 10 96.20 9.16 190 64 LTCCN308M2
21 525 V 12.5 15 144.36 13.75 265 65 LTCCN312M2
22 525 V 15 18 173.23 16.50 265 65 LTCCN315M2
23 525 V 20 24 230.97 21.99 265 84 LTCCN320M2
24 525 V 25 30 288.72 27.49 265 84 LTCCN325M2
25 525 V 30 36 346.46 32.99 230 116 LTCCN330M2
17
Heavy Duty Capacitors - Overall Dimensions
Box Type

5 to 12.5 kVAr 15 to 50 kVAr

2 slot 8 x 10

D1 ± 1
4 slot 8 x 15
Hole Ø22 mm,
Hole Ø30 mm,
for cable entry
W±5 for cable entry
D±5 W±5
D±5

1
1
H±5

H±5
2 2
Embossing Embossing

Power rating Dimensions

Sr. Voltage (kVAr) Capacitance Rated current in (mm)
(uF) (A) Cat. Nos.
No.
50 Hz 60 Hz W D D1 H
1 440 V 1 1 16.44 1.31 125 45 - 170 LTBCH301B2
2 440 V 2 2 32.88 2.62 125 45 - 170 LTBCH302B2
3 440 V 3 4 49.32 3.94 185 60 - 240 LTBCH303B2
4 440 V 4 5 65.77 5.25 185 60 - 240 LTBCH304B2
5 440 V 5 6 82.21 6.56 240 80 - 300 LTBCH305B2
6 440 V 7.5 9 123.31 9.84 240 80 - 300 LTBCH307B2
7 440 V 8.33 10 136.96 10.93 240 80 - 300 LTBCH308B2
8 440 V 10 12 164.42 13.12 240 80 - 300 LTBCH310B2
9 440 V 12.5 15 205.52 16.40 240 80 - 300 LTBCH312B2
10 440 V 15 18 246.62 19.68 240 80 75 300 LTBCH315B2
11 440 V 20 24 328.83 26.24 240 160 75 300 LTBCH320B2
12 440 V 25 30 411.04 32.80 240 160 75 300 LTBCH325B2
13 440 V 30 36 493.25 39.37 240 160 75 300 LTBCH330B2
14 440 V 50 60 822.08 65.61 240 320 150 350 LTBCH350B2
15 480 V 7.5 9 103.62 9.02 240 80 - 300 LTBCH307C2
16 480 V 12.5 15 172.69 15.04 240 80 - 300 LTBCH312C2
17 480 V 15 18 207.23 18.04 240 80 75 300 LTBCH315C2
18 480 V 20 24 276.31 24.06 240 160 75 300 LTBCH320C2
19 480 V 25 30 345.39 30.07 240 160 75 300 LTBCH325C2
20 480 V 30 36 414.47 36.09 240 160 75 300 LTBCH330C2
21 525 V 7.5 9 86.61 8.25 240 80 - 300 LTBCH307M2
22 525 V 12.5 15 144.36 13.75 240 80 - 300 LTBCH312M2
23 525 V 15 18 173.23 16.50 240 80 75 300 LTBCH315M2
24 525 V 20 24 230.97 21.99 240 160 75 300 LTBCH320M2
25 525 V 25 30 288.72 27.49 240 160 75 300 LTBCH325M2
26 525 V 30 36 346.46 32.99 240 160 75 300 LTBCH330M2
27 525 V 33.1 40 382.26 36.40 240 160 75 300 LTBCH333M2
 SUPER HEAVY DUTY CAPACITORS 18
L&T Super Heavy Duty Capacitors are designed and developed to meet reactive
power requirements of modern day industries having higher harmonics. These
metalized polypropylene capacitors ranges from 3-33 kVAr with cylindrical type
construction. They can withstand peak inrush current of 350 times the rated
and an overload withstand capacity of 2.5 times rated current. They have better
harmonic withstand capability and long life along with necessary safety
features like over pressure disconnector and self-healing technology.

For Selection and Application details please refer page no. 80

Technical Details
Series LTCCR
Range 3 - 33 kVAr
Standards IEC 60831-1+2, EN 60831-1+2
Rated frequency 50 Hz
Rated Voltage 440 / 480 / 525 V
Over Voltage +10% (8h/24h), +15% (30m/24h), +20%(5m/24h), +30% (1m/24h)
Over current 2.5 x In
Peak Inrush Current 350 x In
Operating Losses (Dielectric) ≤0.2 W / kVAr
Operating Losses (Total) ≤0.45 W / kVAr
Tolerance on capacitance -5% to +5%
Test Voltage (Terminal-Terminal) 2.15 times rated voltage for 2 s
Test voltage (Terminal-Casing) 5 kV (AC) for 10 s
Degree of protection IP20
Ambient Temperature -40°C to 65°C
Cooling Natural or Forced Air Cooling
Permissible Relative Humidity Max 95%
Maximum Operating Altitude 4000 m above mean sea level
Mounting Universal
Safety features Overpressure Disconnection System, Finger-proof terminals
Impregnation Non-PCB biodegradable Polyuretanne self-extinguishing resin
Casing Aluminum case with bottom fixing M12 x 16
Dielectric Composition Metalized Polypropylene
Terminals Optimized capacitor safety terminals with electric shock protection IP20
Discharge Resistors/Time Incorporated. Standard discharge time 60 seconds.
Switching Operations (maximum) 15000 switchings per year
Life* 2,25,000 hrs at -40/60ºC; 1,50,000 hrs at -40/65ºC

*at standard operating conditions

19
Super Heavy Duty Capacitors - Overall Dimensions
Cylindrical Type

Lable

H
D

M12 x 16

WASHER DIN 6798 A M12

SCREW DIN 936 M12 ZNC

Power Rating (kVAr) Capacitance Rated Current Dimensions (mm)

Sr. No. Voltage (V) Cat Nos.
50 Hz 60 Hz (microF) (A) H D
1 440 3 4 49.32 3.94 260 70 LTCCR303B2
2 440 5 6 82.21 6.56 260 70 LTCCR305B2
3 440 7.5 9 123.31 9.84 260 85 LTCCR307B2
4 440 8.33 10 136.96 10.93 260 85 LTCCR308B2
5 440 10 12 164.42 13.12 260 85 LTCCR310B2
6 440 12.5 15 205.52 16.40 260 100 LTCCR312B2
7 440 15 18 246.62 19.68 260 100 LTCCR315B2
8 440 20 24 328.83 26.24 265 120 LTCCR320B2
9 440 25 30 411.04 32.80 265 136 LTCCR325B2
10 480 7.5 9 103.62 9.02 260 85 LTCCR307C2
11 480 12.5 15 172.69 15.04 260 100 LTCCR312C2
12 480 15 18 207.23 18.04 265 120 LTCCR315C2
13 480 20 24 276.31 24.06 265 120 LTCCR320C2
14 480 25 30 345.39 30.07 265 136 LTCCR325C2
15 480 30 36 414.47 36.08 265 136 LTCCR330C2
16 525 7.5 9 86.61 8.25 260 85 LTCCR307M2
17 525 8.33 10 96.20 9.16 260 85 LTCCR308M2
18 525 12.5 15 144.36 13.75 260 100 LTCCR312M2
19 525 15 18 173.23 16.50 265 120 LTCCR315M2
20 525 20 24 230.97 21.99 265 120 LTCCR320M2
21 525 25 30 288.72 27.49 265 136 LTCCR325M2
22 525 30 36 346.46 32.99 265 136 LTCCR330M2
23 525 33.3 40 384.57 36.62 310 136 LTCCR333M2
 LTXL: ULTRA HEAVY DUTY CYLINDRICAL CAPACITORS 20
L&T LTXL Ultra Heavy duty cylindrical capacitors, like their box counterparts, are
sturdy & specially designed to work in very heavy duty applications and high
harmonics. They have an inrush current withstand capability of 500 times the
rated and an overload withstands capacity of 3 times the rated. In modern
industries with high harmonics and high switching rates, it can be an effective
solution and delivers long life. It has all necessary safety features of standard
capacitors like over pressure disconnector and self-healing technology.

Technical Details
Series LTCCU
Range 5-25 kVAr
Standards IEC 60831-1+2, EN 60831-1+2
Rated frequency 50 Hz
Rated Voltage 440 / 480 / 525 V
Over Voltage +10% (8h/24h), +15% (30m/24h), 20% (5m/24h), +30% (1m/24h)
Overcurrent 3 x In
Peak Inrush Current up to 500 x In
Operating Losses (Dielectric) ≤0.2 W / kVAr
Operating Losses (Total) ≤0.45 W / kVAr
Tolerance on capacitance -5% to + 5%
Test Voltage (Terminal-Terminal) 2.15 times rated voltage for 2 s
Test voltage (Terminal-Casing) 5 kV (AC) for 1 min.
Degree of protection IP20
Ambient Temperature -40°C to 65°C
Cooling Natural or Forced Air Cooling
Permissible Relative Humidity Max. 95%
Maximum Operating Altitude 4000 m above mean sea level
Mounting Universal
Safety features Overpressure Disconnection System, Finger-proof terminals
Impregnation Non-PCB biodegradable Polyurethane self-extinguishing resin
Casing Aluminum case with bottomfixing M12 x 16
Dielectric Composition Metalized Polypropylene
Terminals Optimized capacitor safety terminals with electric shock protection IP20
Discharge Resistors/Time Through Resistor. Standard discharge time 60s
Switching Operations (maximum) 18000 switchings per year
Life* 2,00,000 hrs at 65ºC

*at standard operating conditions

21
LTXL: Ultra Heavy Duty Capacitors - Overall Dimensions

Cylindrical Type

Lable

M12 x 16

WASHER DIN 6798 A M12

SCREW DIN 936 M12 ZNC

Power Rating (kVAr) Capacitance Rated Current Dimensions (mm)

Sr. No. Voltage (V) Cat Nos. Weight (kg)
50 Hz 60 Hz (microF) (A) H D
1 440 5 6 82.21 6.56 395 70 LTCCU305B2 1.6
2 440 7.5 9 123.31 9.84 395 85 LTCCU307B2 2.3
3 440 8.33 10 136.96 10.93 395 85 LTCCU308B2 2.3
4 440 10 12 164.42 13.12 395 100 LTCCU310B2 3.1
5 440 12.5 15 205.52 16.40 395 100 LTCCU312B2 3.1
6 440 15 18 246.62 19.68 400 120 LTCCU315B2 4.6
7 440 20 24 328.83 26.24 400 120 LTCCU320B2 4.5
8 440 25 30 411.04 32.80 400 136 LTCCU325B2 5.8
9 480 7.5 9 103.62 9.02 395 85 LTCCU307C2 2.2
10 480 8.33 10 115.08 10.02 395 100 LTCCU308C2 3.1
11 480 10 12 138.16 12.03 395 100 LTCCU310C2 3.0
12 480 12.5 15 172.69 15.04 400 120 LTCCU312C2 4.6
13 480 15 18 207.23 18.04 400 120 LTCCU315C2 4.5
14 480 20 24 276.31 24.06 400 136 LTCCU320C2 5.8
15 525 7.5 9 86.61 8.25 395 100 LTCCU307M2 3.1
17 525 10 12 115.49 11.00 395 100 LTCCU310M2 3.0
18 525 12.5 15 144.36 13.75 400 120 LTCCU312M2 4.5
19 525 15 18 173.23 16.50 400 120 LTCCU315M2 4.4
20 525 20 24 230.97 21.99 400 136 LTCCU320M2 5.6
 LTXL: ULTRA HEAVY DUTY BOX CAPACITORS 22
The LTXL range of capacitors are designed for Ultra heavy duty
applications and can withstand heavy load fluctuations, high
inrush current and harmonics.

Applications
Applications such as welding, steel rolling, etc., with heavy
n

load fluctuations and high thermal loading

Systems with high harmonic distortion levels
n

Systems with high inrush current

n

Best suited for detuned harmonic filter

n

Features
Long life expectancy (upto 300000 hrs)
n

Maximum inrush current withstand capability (upto 500 times IR)

n

Low power loss (0.35 W/kVAr)

n

Protection with internal fuse

n

The life of a capacitor largely depends upon its operating temperature. LTXL box type capacitors use advanced APP
technology. By employing thicker aluminum foil, thicker hazy polypropylene film and special impregnates, LTXL box
type capacitor is able to operate at lower temperatures and hence achieve a longer life. These capacitors are thus able
to withstand stringent operating conditions. The higher surface area and special epoxy based coating also ensures
better heat dissipation. The capacitor is designed to operate at case temperature up to 70 oC.

In LTXL box, two polypropylene films and two Al films

1. Al Film are grouped together as shown in the figure. The
2. Polypropylene Film wave-cut and heavy edge metalized films are then
3. Electric Contact (schooping) rolled to form a capacitor element. Many such
4. Bare PP Film Edge capacitor elements are pressed and stacked together
1 and are internally connected in parallel. Depending
upon the rating of the capacitor, the number of stacks
differ. These stacks are placed inside a case and are
vacuum impregnated with non-PCB, biodegradable
3 4 2 4 3 oil (PXE).

Design of LT Capacitor Each capacitor element is protected by an internal fuse

as shown in the figure. If there is an internal short
circuit in any of the capacitor element, the fuse of that
corresponding capacitor element blows.

Fuse Capacitor For Selection and Application details please refer page
element no. 80

Blown fuse
23
Technical Details

LTXL - Ultra Heavy Duty Box

Series LTBCU

Range 5 - 50 kVAr

Standards IS 13585 (Part 1)-2012, IEC 60931-1 1996

Rated Frequency 50 Hz

Rated Voltage 415 / 440 / 480 / 525 / 690 V

Over Voltage +10% (8h/24h), +15% (30m/24h), +20% (5m/24hrs), +30% (1m/24hrs)

Overcurrent Upto 3 x In

Peak Inrush Current Upto 500 x In

Operating Losses (Dielectric) < 0.2 W / kVAr

Operating Losses (Total) < 0.35 W / kVAr

Tolerance on Capacitance -5 / +10% as per IS

Test Voltage (Terminal-Terminal) 2.15 times rated voltage for 10 sec

Test Voltage (Terminal-Casing) 3 kV (AC) for 1 minute

Degree of Protection IP20, Indoor mounting (IP54 optional)

Ambient Temperature -25 / D (Case temperature 70ºC)

Cooling Natural or forced air cooling

Permissible Relative Humidity Max 95%

Maximum Operating Altitude 4000 m above sea level

Mounting Upright

Safety Features Internal fuse

Impregnation Non-PCB PXE oil, Biodegradable oil

Casing MS sheet metal with special black Epoxy coating

Dielectric Composition Biaxially oriented polypropylene film with aluminium foil electrode

Terminals Ceramic bushing

Discharge Resistors / Time Discharge resistors fitted, Standard discharge time 60 seconds

Switching operations (maximum) 20000 Switchings per year

Life* 3,00,000 hrs

*at standard operating conditions

 24
LTXL: Ultra Heavy Duty Capacitors - Overall Dimensions

Box Type
M-10 Threaded
brass terminal
60 60
7
10

65
5

Top cover 4
250 125

H
115

6 3

Ø30 mm Hole
2
Elevation End View
1
L w
L1
End View
Elevation

Power rating Rated Dimensions

Sr. Voltage (kVAr) Capacitance current in (mm) Weight (kg)
(uF) Cat. Nos.
No. (A)
50 Hz 60 Hz L L1 W H
1 440 V 5 6 82.21 6.56 240 270 115 115 LTBCU305B2 5.5
2 440 V 7.5 9 123.31 9.84 240 270 115 150 LTBCU307B2 7.5
3 440 V 8.33 10 136.96 10.93 240 270 115 150 LTBCU308B2 8.0
4 440 V 10 12 164.42 13.12 240 270 115 175 LTBCU310B2 10
5 440 V 12.5 15 205.52 16.40 240 270 115 200 LTBCU312B2 11
6 440 V 15 18 246.62 19.68 240 270 115 225 LTBCU315B2 12
7 440 V 20 24 328.83 26.24 240 270 115 275 LTBCU320B2 14
8 440 V 25 30 411.04 32.80 240 270 115 325 LTBCU325B2 16
9 440 V 30 36 493.25 39.37 240 270 115 375 LTBCU330B2 18
10 440 V 50 60 822.08 65.61 240 270 115 575 LTBCU350B2 28
11 480 V 7.5 9 103.62 9.02 240 270 115 150 LTBCU307C2 7.5
12 480 V 10 12 138.16 12.03 240 270 115 150 LTBCU310C2 8
13 480 V 12.5 15 172.69 15.04 240 270 115 175 LTBCU312C2 10
14 480 V 15 18 207.23 18.04 240 270 115 200 LTBCU315C2 11
15 480 V 20 24 276.31 24.06 240 270 115 250 LTBCU320C2 13
16 480 V 25 30 345.39 30.07 240 270 115 300 LTBCU325C2 15
17 480 V 30 36 414.47 36.09 240 270 115 325 LTBCU330C2 16
18 525 V 7.5 9 86.61 8.25 340 370 115 115 LTBCU307M2 8
20 525 V 12.5 15 144.36 13.75 340 370 115 150 LTBCU312M2 10
21 525 V 15 18 173.23 16.50 340 370 115 175 LTBCU315M2 11
22 525 V 20 24 230.97 21.99 340 370 115 200 LTBCU320M2 13
23 525 V 25 30 288.72 27.49 340 370 115 250 LTBCU325M2 16
24 525 V 30 36 346.46 32.99 340 370 115 275 LTBCU330M2 18
25 525 V 33.1 40 382.26 36.40 340 365 115 325 LTBCU333M2 20
 HARMONICS 26
Harmonics is defined as a component of periodic wave (or a signal) whose frequency is integral multiple of the
fundamental frequency. Non linear loads such as rectifiers, inverters, variable speed drives, furnaces, etc. create
harmonics.
These currents consist of a fundamental frequency component rated at 50 Hz, plus a series of overlapping currents,
with frequencies that are multiples of the fundamental frequency. The result is deformation of the current (and, as a
consequence, voltage) that has a series of associated secondary effects.

+ + +... =

Fundamental Harmonic wave of Harmonic wave of Distorted wave

th th
Wave 50 Hz 5 order 250 Hz 7 order 350 Hz

Types of Harmonic Loads

Type of Load Wave Shape Harmonic Spectrum THD - I

100

%Magnitude wrt fundamental

• 6 Pulse and 12 Pulse drive* 80

(VFD & UPS) 60

0.0
• Three-phase / Single-phase 40

rectifiers 0.0
20

• Arc / Induction furnace 0

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic number

100
%Magnitude wrt fundamental

• Discharge lamps / CFL 80

• Single-phase converters 60

• Computer, IT loads 0.0

40

• SMPs 20

• TVs 0
1 3 5 7 9 11 13 15 17
Harmonic number

* Higher the number of pulses, lesser is the harmonic distortion

Ill Effects of Harmonics

Type of Equipment Effect of Harmonics

Increased power losses, over heating due to skin effect

as higher frequency current flows on cable periphery
Rotating Machines
increasing cable resistance, pulsating torque due to
negative phase sequence harmonics
Transformer, Switchgear, Power Cables Over-heating, increased power consumption
Protective Relays Mal-operation, nuisance tripping
Power Electronics Mal-operation, failure
Power Capacitors High currents & failure due to overload

The above malfunctions are not always felt immediately after the system is installed, but the effects may be felt in the
long term and are difficult to distinguish from the natural ageing of equipment. Hence it is important to have some
basic knowledge about harmonics and find solutions for the same.
27 HARMONIC AMPLIFICATION
Harmonic amplification is an undesired increase in the magnitude of harmonics beyond the level that is being
generated in the system. This in turn amplifies the ill effects of the harmonics. The article briefs how the amplification
happens in the network and solutions to avoid this amplification.
Power capacitors are added to the network for improving the power factor. The addition of capacitors results in
reduction of system impedance. Capacitive impedance is inversely proportional to frequency (as shown in the figure 1).

Hence the capacitor offers lower impedance for high frequency (250
Hz, 350 Hz, 550 Hz and so on). This results in increase in the magnitude
of harmonic currents. This can be practically seen by measuring
harmonics at a particular location in the electrical network with and
without power factor correction capacitors (APFC panels).
Following are the snapshots of harmonic measurement done at the
main incomer, with and without capacitors.

Figure 2: Measurement with APFC Panel OFF

In this case, the power factor,

obviously, will be poor. But the
harmonic contents are very much
within the limit (overall I-THD
around 3.5% and 5th harmonic
around 2%)

Figure 3: Measurement with APFC Panel ON

As soon as the power factor

correction capacitors are
connected, the THD value shoots
up. The overall I-THD increased
th
from 3.5% to 22% and 5
harmonic increased from 2% to
17%. The absolute magnitude of
5th harmonic amplified from 16 A
to 144 A. The distortions in the
waveform also indicate the same.

In the above equation (1), for the same set of harmonic frequencies, on adding more capacitors for PF improvement,
the capacitive impedance (XC) will drop further. Again this will result in amplification of the harmonics. If the power
factor goes to leading, the amplification will be worse. The unnecessary amplification of harmonics damages power
capacitors and over heats switchgear, cables and busbars.

The solutions to prevent harmonic amplification are:

• By connecting a series inductor, so as to form a detuned filter (series LC), the impedance increases, when the
frequency increases (as XL = 2 pfL). The impedance will be high for high frequency harmonics and no
amplification will happen. Hence, the THD (with reactor + capacitor) will be less than or equal to the earlier
THD levels with no capacitors

• By strictly avoiding leading power factor, the excess addition of capacitors can be prevented and hence the
amplification because of this can also be avoided. The optimum power factor of 0.97 to 0.99 should always be
maintained always
 HARMONIC RESONANCE 28
Many industries may not generate high harmonics. Sometimes harmonic resonance occurring between power
capacitors and transformers causes very high magnification of harmonics. This causes increased rate of failures and
over-heating of electrical equipments. This article briefs about the basics of harmonic resonance, a practical case
study and solution to avoid resonance.

In a system with inductive (XL) and capacitive (XC ) impedances, resonance can happen at one particular frequency
(resonant frequency, FR). At this point XL is equal to XC and the net impedance is very low. Hence, at resonance point,
the magnitude of the current (with frequency FR) will be maximum and only inherent resistance in the network would
limit the current.

In practical network, the resonance is possible because of one of the

following reasons:
• Parallel resonance within a given electrical system, involving internally
generated harmonics (in the load) and resonance between local
capacitors and the predominantly inductive supply (transformers)
• Series resonance involving external harmonics (in the supply system)
and resonance between capacitors within electrical system
• Interactive resonance between different harmonics filters within a given
electrical network
z)

Typically, the inductance (L, of the transformer)in the system remains almost constant, but the capacitance(C) is
varied (in steps) as per the requirement to maintain higher power factor. So, when the capacitance increases the
resonant frequency (FR) drops, as FR is inversely proportional to square root of capacitance.

1
Resonant frequency FR =
2 LC

The lower resonant frequency is dangerous, as it may match with any of the predominant harmonics and cause more
damage. Let us see a practical case study of resonance happening between variable PFC capacitors (C) and
transformer.
Consider an industry with 1000 kVA transformer of %Z = 5.67% and 750 kVAr APFC panel. The resonant frequency
can be calculated from the formula:

kVASC
Resonant frequency = FS x
kVAr
Where FS is the System frequency = 50 Hz
1000
kVASC is the short circuit power of the transformer = kVA = = 17636kVA
%z
100 0.0567
kVAr is the power rating of the capacitor connected under the transformer for power factor correction.

Case 1: When 145 kVAr is Connected to the System,

Resonant frequency = 50 x 17636 = 550Hz

145
29
This frequency exactly matches with 11th harmonic (550 Hz) and results in resonance. Following is the harmonics
measurement that depicts the 11th harmonic resonance, where it increases from less than 5% to 25%. This huge
amplification will damage the capacitor and other equipments.

49.73 Hz 21 / 07 /11 16:36 70% 49.73 Hz 21 / 07 / 11 17:34

Ah 11 1 4.9% 2 5.0% 3 5.1% 1 27.5% 2 26.6% 3 22.1%

18.7 A 19.2 A 19.9 A Ah 11 103.1A 99.3A 81.3A
+ 122 ° +112° + 107° -137º +112º +107º

% %
100 100

50 50
11th harmonic
resonance

1 3 5 7 9 11 13 15 17 19 21 23 25 1 3 5 7 9 11 13 15 17 19 21 23 25

Figure 1: Measurement with APFC Panel OFF Figure 2: Measurement with APFC PanelON

Case 2: When 250 kVAr of Capacitor is Switched on in the Same Industry,

17636
Resonant frequency = 50 x = 420Hz
250

In this case, no resonance will happen; hence the amplification level will be less than the case1. If harmonics study is
carried at this particular moment, the system would reveal relatively lesser harmonics level (%I-THD)

Case 3: When 700 kVAr is Connected to the System,

17636
Resonant frequency = 50 x = 250Hz
700

Once again, this frequency perfectly matches with 5th harmonic. Typically 5th harmonic is the least order harmonic with
higher magnitude (6 pulse drives). Resonance at this harmonic order would result in even worse damage than the case 1.

From the above cases it is evident that any peculiar problem like frequent failure of capacitors, nuisance tripping of
MCCBs, frequent blowing of fuses and over-heating of busbars is, may be because of harmonic resonance. Resonance or
worst case THD may not be revealed at the moment of harmonic measurement or troubleshooting. Hence at times,
finding the root cause of any such failures is very difficult.

Solution for harmonic resonance is to detune, by using a reactor in series with each capacitor. This detuned filter will
forcefully create one resonant frequency, so that the combination offers higher impedance for high frequency
harmonics. For example, installation of 7% reactor with each capacitor in APFC panel, will create tuning frequency at
th
189 Hz. Hence, resonance at harmonic frequencies (5 harmonics and above) can be avoided. Moreover, all the
harmonics having frequency above 189 Hz (i.e., from 5th harmonics onwards) will lie in inductive region, where the
impedance increases when the frequency increases (XL = 2p fL). One important point to note is that all the capacitors in
the industry must have similar series inductor; else the overall tuning frequency may not be at 189 Hz.
INTERPRETATION OF TOTAL HARMONIC DISTORTION (THD) 30
It's a known fact that harmonics cause over loading of power capacitors and consequently reduce the life of power
capacitors. Normally lot of emphasis is given only to %THD for assessing the harmonics level while the frequency
th th th th
spectrum (5 , 7 , 11 , 13 and so on) of the harmonics are not given due importance.
The over-current (and hence the stress on the capacitors) will not only depend on the %THD value but also on the
magnitude of individual harmonics, which can be clearly seen in the frequency spectrum. Following calculations prove
the above statement.

Case 1:
Assumptions:
1. VTHD : 25%
2. Harmonic frequencies considered: 5th (250 Hz), 7th (350 Hz)
3. V5=20%V1 and V7=15%V1
4. All other harmonic frequencies are negligible
5. The capacitors are delta connected hence will not provide a path for the third harmonic to flow
Important Formulae:

where XC is the capacitive reactance, f is the frequency, C is the capacitance IC=VC / XC, where IC is the capacitive current, VC is
the voltage across the capacitor and XC is the capacitive reactance

S
(Vi ) / V1), where i=3 to 99

Calculations:
Using the superposition theorem, we can calculate the current contribution of individual harmonic voltages.

5 = V5 / Xc5 = 0.2V1/[1/(2 x p
I x 5 x f x C)] = 0.2 x 5 x V1/Xc1 = 1 x V1/Xc1 = I1

Similarly,
I7 = 1.05I1
The total current I will be a vector sum of I1, I5 and I7

I + I + I )(
( 1+1+1.1025 x I )
Thus I = 2 2 = 2 1
1 5 7

Net current, I =1.8 I1 -----------------------> (1)

Case 2:
Assumptions:
1. VTHD: 25%
2. Harmonic frequencies considered: 5th (250 Hz), 7th (350 Hz), 11th (550 Hz), 13th (650 Hz)
3. V5 =18%V1, V7 =15%V1, V11 =8%V1 and V13 =4%V1

Calculation:
I5 = V5 / Xc5 = 0.18V1 / [1/(2 x p
x 5 x f x C)] = 0.18 x 5 x V1 / Xc1 = 0.9 x V1 / Xc1 = 0.9I1
Similarly,
I7 = 1.05I1 I11 = 0.88I1 and I13 = 0.52I1
The total current I will be a vector sum of I1, I5, I7, I11 and I13

Thus I = I 12 + 152 + I 27 + I 11
2 2
+ I 13 = 12+0.92+1.052+0.882+0.522 x I1
Net current, I =2 I1 -----------------------> (2)
Thus, in the above two cases, even the THD value remains same (25%), the net rms current (ref. Eq 1 and Eq 2) value is
different depending upon the spectral values.
Hence THD value and detailed information of the frequency spectrum are necessary to predict the capacitor over-
current. Harmonics study is the best way to get the frequency spectrum details and hence the exact over current
value can be calculated.
31 UNDERSTANDING CURRENT & VOLTAGE HARMONICS
Current and voltage harmonics are often used interchangeably. At most places, only harmonics is quoted and
whether the values pertain to current or voltage is not mentioned. The differentiation can be done on the basis of
their origin.

Understanding Total Harmonic Distortion

The current and voltage harmonics in a system are often expressed as Total Harmonic Distortion (THD). The total
harmonic distortion, or THD, of a quantity is a measurement of the harmonic distortion present and is the ratio of all
harmonic components to the fundamental component. It is given by the formula as under:

Y1 is the rms value of fundamental

Where, th
Yh is the rms value of h harmonic

Hence, current THD is the ratio of the root-mean-square value of the harmonic currents to the fundamental current.

Where do Current & Voltage Harmonics Originate?

Harmonics always originate as current harmonics and voltage harmonics are the results of current harmonics.
Current harmonics originate because of the presence of non-linear loads like variable speed drives, inverters, UPS,
television sets, PCs, semiconductors circuits, welding sets, arc furnaces in the system. They act as harmonic current
sources. The resulting current waveform can be quite complex depending on the type of load and its interaction with
other components of the system.

Linear load

Non-linear load

Fig 1: Linear & Non-Linear Loads

The distorted current waveforms can be represented as the sum of current waveform of fundamental frequency and
of its multiples (harmonics):

¥
2 4 ¦
(t)=å t+j
h=1(Ch Sin(hw
o h))
1

1
Where,
ch - Magnitude of nth order harmonics
0
- Phase angle of nth order harmonics
90 180 270 360

2
-1 Fig 2: Current waveform as sum of fundamental frequency
3 component and its multiples

-2
 32
Voltage harmonics do not originate directly from non-linear loads. The current harmonics (distorted waveform) flow
through system impedance (source and line impedances) and cause harmonic voltage drop across the impedances.
This will distort the supply voltage waveform. Thus voltage harmonics are generated. Long cable runs, high
impedance transformers, etc. contribute to higher source impedance and hence, higher voltage harmonics.
A typical power system has the following impedances as indicated in the line diagram:

Grid Z Gh

Transformer Z Th

lh

Z Th Z Ch
Cable Z Ch

Non-Linear
Load
lh Z Sh

Sinusoidal Vthd @ Vthd @ Vthd @

Non-Linear Load Voltage Grid Transformer Load
Source
Harmonic
Current
Source

Fig 3: Impedance in a power system

In the above diagram,

Vh = hth harmonic voltage
th
Ih = h harmonic current
th
Zh = Impedance at h harmonic
Vthd = Voltage total harmonic distortion

At load, Vh= Ih x (ZCh + ZTh + ZGh)

At transformer, Vh= Ih x (ZTh + ZGh)
At grid, Vh= Ih x (Zgh)

Usually, grid impedances are very low and hence, the harmonic voltage distortions are also low there. However, they
may be unacceptably higher on the load side as they are subjected to full system impedance there. Hence, it becomes
important where the harmonics measurements are done.
However, in case of DG sets, the source impedance is large resulting in high voltage harmonics despite small current
harmonics. Thus, a clear distinction between current and voltage harmonics becomes important here.
33
An industry, say industry A, that has large non-linear loads will generate huge current harmonics in its system. A
nearby industry, say industry B, connected to the same grid may not have non-linear loads, yet, it may be subjected to
high voltage harmonics. These voltage harmonics are the result of high current harmonics of industry A and
impedance of grid & transformer. Thus, industry B despite small current harmonics, has high voltage harmonics.
However, if industry B goes for power factor correction, then, due to the presence of capacitors, current harmonics
may also appear in the system, magnifying voltage harmonics further.

How do Current & Voltage Harmonics Affect the System?

Current harmonics increase the rms current flowing in the circuit and thereby, increase the power losses. Current
harmonics affect the entire distribution all the way down to the loads. They may cause increased eddy current and
hysteresis losses in motor and transformers resulting in over-heating, overloading in neutral conductors, nuisance
tripping of circuit breakers, over-stressing of power factor correction capacitors, interference with communication
etc. They can even lead to over-heating and saturation of reactors.
Voltage harmonics affect the entire system irrespective of the type of load. They affect sensitive equipment
throughout the facility like those that work on zero-voltage crossing as they introduce voltage distortions.

Understanding IEEE 519 Guidelines

The purpose of harmonic limits in a system is to limit the harmonic injection from individual customers to the grid so
that they do not cause unacceptable voltage distortion in the grid. IEEE 519 specifies the harmonic limits on Total
Demand Distortion (TDD) and not Total Harmonic Distortion (THD). TDD represents the amount of harmonics with
respect to the maximum load current over a considerable period of time (not the maximum demand current),
whereas, THD represents the harmonics content with respect to the actual load current at the time of measurement.
It is important to note here that a small load current may have a high THD value but may not be significant threat to
the system as the magnitude of harmonics is quite low. This is quite common during light load conditions.
TDD limits are based on the ratio of system's short circuit current to load current (ISC/ IL). This is used to differentiate a
system and its impact on voltage distortion of the entire power system. The short circuit capacity is a measure of the
impedance of the system. Higher the system impedance, lower will be the short circuit capacity and vice versa.

The Guidelines IEEE 519-2014 at PCC Level are as under:

Current distortion limits for General Distribution systems (120V Through 69 kV)

Maximum Harmonic Current Distortion in %IL

Individual Harmonic Order (Odd Harmonics)

ISC/IL 3≤h<11 11≤h<17 17≤h<23 23≤h<35 35≤h≤50 TDD

<20 4.00% 2.00% 1.50% 0.60% 0.30% 5.00%

20-50 7.00% 3.50% 2.50% 1.00% 0.50% 8.00%

50-100 10.00% 4.50% 4.00% 1.50% 0.70% 12.00%

100-1000 12.00% 5.50% 5.00% 2.00% 1.00% 15.00%

>1000 15.00% 7.00% 6.00% 2.50% 1.40% 20.00%

where
Isc = maximum short-circuit current at PCC [Can be calculated as MVA/(%Z x V)]
IL = maximum demand load current (fundamental frequency component) at PCC
 34
Systems with higher ISC/ IL have smaller impedances and thus they contribute less in the overall voltage distortion of
the power system to which they are connected. Thus, the TDD limits become less stringent for systems with higher ISC/
IL values. In other words, higher the rating of transformer used for the same amount of load, higher will be the
allowable current distortion limits.

Voltage distortion limits

Bus Voltage at PCC Individual Voltage Distortion VTHD

V ≤ 1.0 kV 5.00% 8.00%

1 kV ≤ V ≤ 69 kV 3.00% 5.00%

69 kV ≤ V ≤ 161 kV 1.50% 2.50%

> 161 kV 1.00% 1.50%

The limits on voltage are set at 5% for total harmonic distortion and 3% of fundamental for any single harmonic at
PCC level. Harmonics levels above this may lead to erratic functioning of equipment. In critical applications like
hospitals and airports, the limits are more stringent (less than 3% VTHD) as erroneous operation may have severe
consequences. As discussed already, the harmonic voltage will be higher downstream in the system.

Solutions for Current & Voltage Harmonics

Current Harmonics Voltage Harmonics
(VTHD) Recommended Solutions**
(ITHD)

High Detuned Harmonic Filter with (SHD / LTXL )480 V Capacitors and/or
Low (£
5%)
Active Harmonic Filter

High High (>5%) Active Harmonic Filter and 525 V (SHD / LTXL Cyl) Capacitors

Grid may be polluted with imported voltage harmonics. It may not be

Low High (>5%)
possible to reduce them at the load side. Check with utility to rectify

**These are typical solutions. However the actual solution may vary depending up on the actual harmonic content in the system.
35 TRIPLEN HARMONIC MITIGATION
Triplen harmonics have frequencies in odd multiples of 3, i.e., 3rd harmonic (150 Hz), 9th harmonic (450 Hz), 15th
harmonic (750 Hz) and so on. These harmonics have some peculiar characteristics, which make them very difficult to
handle and mitigate. This article explains about the basics, sources, effects and mitigation techniques of triplen
harmonics.

Sources of Triplen Harmonics

Triplen harmonics are usually generated by single phase non-linear loads that share a common neutral. Some of
them are,
• SMPS in computers, televisions, etc.,
• CFL lamps
• Electronic dimmers and so on
These types of loads are common in IT parks, office, hospital and other commercial buildings. Following are the
typical current harmonic spectra of SMPS and CFL lamps, where third harmonic is predominantly high.

Y R
Y
B

B
Positive sequence Zero sequence

Neutral current is the vector sum of all the three phase (120o phase displaced) and the sum is zero, if the loads are
balanced in all the three phase. But the presence of triplen harmonics will result in the flow of neutral current, even if
the loads are balanced. This phenomenon is explained below:

100 100
% Magnitude wrt fundamental

% Magnitude wrt fundamental

80 80

60 60

40 40

20 20

0 0
1 3 5 7 9 11 13 15 17 1 3 5 7 9 11 13 15 17
Harmonic number Harmonic number
SMPS CFL

All the triplen harmonics are zero sequence in nature and they are exactly in-phase in all the three phases, where as
the fundamental component (50 Hz), has positive phase sequence, displaced by 120o between the three phases.
 36
The accumulated neutral current, because of the additive triplen current, can go up to 200% of the phase current.

Three Phase System

Time R- Phase
Wave forms of balanced three phase
fundamental currents

Time
Y- Phase
R-Phase current with its third
harmonic component

Time B- Phase
Y-Phase current with its third
harmonic component

Time A
d
d
it
i
ono
f
th
i
rdh
a
r
mo
ni
csi
nne
u
t
ra
l
con
d
uc
t
o
r

B-Phase current with its third

harmonic component

Time Third harmonic current of R,Y & B Phases

are in-phase with each other and hence
adds up, without cancellation in the
neutral conductor

Reaching maximum at the same time

Ill Effects of Triplen Harmonics

• The harmonics accumulate in neutral and cause hot neutral or neutral burning due to neutral over-loading.
Thus, we need to use a higher sized cable for neutral
• Distribution transformer over heating
• Busbars and cable overheating due to skin effect
• Eddy current losses (as eddy current is proportional to square of the frequency)
• Reduced life of electrical equipments like transformers, power capacitors, switchgear, etc.

Triplen Harmonic Mitigation

Most commonly used passive filter for triplen harmonics is 14% detuned filter. This filter has the tuning frequency of
133 Hz, which is below the 3rd harmonic (150 Hz). This filter is very effective in averting the harmonic amplification of
3rd harmonics & above and thereby protecting power capacitors and other equipments. But detuned filter does not
eliminate the harmonics completely. In order to achieve that, active harmonic filters with three-phase four-wire
configuration should be used.
37 HARMONIC MITIGATION
Benefits of Harmonics Mitigation
n Reduction in operating expenses
Harmonic mitigation contributes to reduced power losses in transformers, cables, switchgear. Harmonic
mitigation helps in reducing the energy losses

n Reduction in capital expenditure

Harmonic mitigation reduces the r.m.s. value of the current and it eliminates the need to oversize transformers
and hence switchgear, cables and busbars

n Improved business performance

Harmonics are responsible for increased line currents, resulting in additional power losses and increased
temperature in transformers, cables, motors, capacitors. The consequence may be the unwanted tripping of
circuit breakers or protection relays. This might cause significant financial losses linked to a process interruption

Solutions for Harmonic Mitigation

For any electrical system, which is expected to be harmonics rich, it is recommended to study the harmonics level,
analyze and then a proper solution should be employed.

The different solutions employed are as follows:

Harmonic
Filters

Passive Hybrid
Active

Detuned Tuned Active: IGBT-based power

converter that reduces harmonic
distortion

Hybrid: Combination of passive

7% 14% Mitigates harmonics by acting as and active filters
a sink
Merits:
Merits: üReduces THD within IEEE limits
Series LC combination helps in üReduces %THD üDynamic correction of THD is
avoiding harmonic resonance and possible
amplification Demerits: üImproves Distortion PF
û Tuning efficiency is üLoad balancing and
Merits: susceptible to system Displacement PF improvement
üSimple and economical frequency & load variations possible
leading to overheating & üModular – Can be expanded
Demerits: failure of filter along with the load
û Marginal reduction of %THD û Extensive harmonic audit is
û High VTHD will affect the mandatory before
performance installation
 DETUNED FILTERS 38
Detuned Filters are a combination of series inductors and power factor correction capacitors that are meant to:
1. Prevent resonance
2. Prevent harmonic amplification
3. Protect power factor correction capacitors from overload
Typically a detuned filter has a series connected capacitor and reactor. The capacitor terminal voltage varies with
respect to the tuning factor (%p) of the reactor. Tuning factor (%p) is the ratio of inductive impedance to the
capacitive impedance (XL / XC ). Common tuning factors of detuned filters are 7% and 14%.
Every series LC combination behaves capacitive below its tuning frequency [fres = 1/ (2p
LC)] and inductive above. The
inductive element of the detuned filter is selected such that the tuning frequency of the filter is significantly lower
than the lowest order harmonic frequency present in the system. The filter is thus ‘detuned'. The ratio of inductive
reactance (XL) and capacitive reactance (XC) is known as the tuning factor.
A tuning factor of 7% implies XL / XC = 0.07.
The tuning frequency using tuning factor can be calculated as:

fs Where,
ft = fs = Supply Frequency = 50 Hz
p/100 For tuning factor of 7%,ft = 189 Hz.
Impedance (Z)

As can be seen from the above graph, for all frequencies above the
tuning frequency (ft), the combination will provide increasing
impedance. The combination will not provide a low impedance path for
harmonics that the capacitor did earlier, thus preventing harmonic
amplification. Further as the tuning frequency of the combination is
lower than the lowest order harmonic in the system, there is no question
of resonance. At 50 Hz the combination behaves capacitive and power
factor correction is achieved.
ft Frequency

I
The voltage that appears across the terminals of a
capacitor increases the moment you connect an inductor VL
in series with it. This can be illustrated by the below
I
phasor: VL
VS : System Voltage; VC : Voltage across the capacitor; VL :
Voltage across the inductor; I : current. VS VS
As can be seen VC > VS by an amount VL. Thus if reactors VC = VS + VL
are to be added to an existing APFC panel, the capacitors VC
will have to be replaced with those capable of VC
withstanding higher voltages. More over, the output of
the capacitors will have to compensate for the reactive
power that will be consumed by the reactor.

Secondly reactors are a major source of heat. The existing panel may not have sufficient space or cooling
arrangement to handle the heat generated by the newly installed reactors. For these reasons, it is not advisable to
add detuned reactors to existing APFC panels.
Hence, it is difficult to solve harmonics related problems, once the power factor correcting capacitors are installed.
It is thus important to incorporate harmonic mitigation techniques in the system design stage itself.
39
Selection of Capacitor - Reactor Combination for Detuned Harmonics Filters
Typically a detuned filter has a series connected capacitor and reactor. The capacitor terminal voltage varies with
respect to the tuning factor (%p) of the reactor. Tuning factor (%p) is the ratio of inductive impedance to the
capacitive impedance (XL / XC). Common tuning factors of detuned filters are 7% and 14%.
The voltage that appears across the terminals of a capacitor increases the moment an inductor is connected in series.
The actual amount of voltage increase can be calculated using the following formula:

VS
VC =
%p
(1 - )
100

†
For example, the capacitor terminal voltage with 7% detuned reactor shall be calculated using the above
formula:

440
VC =
7
(1 - )
100 VC = 473 V

Hence the rated voltage of the capacitor should be selected as 480 V when used along with 7% reactor. Sometimes,
the voltage variations, as per the electricity board voltage limits, may cause the supply voltage to exceed 480 V. Also,
due to harmonics, both peak and rms voltage may go beyond 480 V. In such cases, a 525 V capacitor should be used
along with 7% detuned reactor. Selection for both 480 V and 525 V capacitor with 7% reactor is given in the table.
†
When 14% reactor is used along with the capacitor, the capacitor terminal voltage,

440
VC =
14
(1 - )
100 VC = 512 V

Here the capacitor should be rated for 525 V when used along with 14% reactor.

Capacitor voltage and kVAr selection for both 7% and 14% reactors are given below:

With 7% detuned reactor With 14% detuned reactor

Effective
kVAr Reactor Reactor
output (440 V) Capacitor (480 V)** Capacitor (525 V)** (440 V) Capacitors (525 V)**

5 kVAr 5 kVAr 7.5 kVAr 480 V 7.5 kVAr 525 V 5 kVAr 7.5 kVAr 525 V

10 kVAr 10 kVAr 12.5 kVAr 480 V 12.5kVAr 525 V 10 kVAr 12.5 kVAr 525 V

12.5 kVAr 12.5 kVAr 15 kVAr 480 V 15 kVAr 525 V 12.5 kVAr 15 kVAr 525 V

15 kVAr 15 kVAr 20 kVAr 480 V 20 kVAr 525 V 15 kVAr 20 kVAr 525 V

20 kVAr 20 kVAr 25 kVAr 480 V 25 kVAr 525 V 20 kVAr 25 kVAr 525 V

25 kVAr 25 kVAr 30 kVAr 480 V 33.3 kVAr 525 V 25 kVAr 30 kVAr 525 V

50 kVAr 50 kVAr 2 nos of 30 kVAr 480 V 2 nos of 33.3 kVAr 525 V 50 kVAr 2 nos of 30 kVAr 525 V

75 kVAr 75 kVAr 3 nos of 30 kVAr 480 V 3 nos of 33.3 kVAr 525 V 75 kVAr 3 nos of 30 kVAr 525 V

100 kVAr 100 kVAr 4 nos of 30 kVAr 480 V 4 nos of 33.3 kVAr 525 V 100 kVAr 4 nos of 30 kVAr 525 V

** Capacitor kVAr selection is done considering the tuning frequency (189 Hz with 7% and 133 Hz with 14%), reactor current and standard capacitor ratings available.
IMPORTANCE OF USING THE RIGHT DETUNED REACTOR 40
Electrical networks often contain significant levels of harmonic distortion, which has led the large majority of
manufacturers of automatic capacitor banks to unanimously include detuned filter units in their offerings. In this
article, we will try to explain the impact of different detuned filters and the consequences of a poor choice, as well as
the recommendation for avoiding these possible risks.

The Importance of Tuning Frequency in Capacitor Banks

There is no such unanimity in the choice of the tuning frequency of the detuned filter offered as standard.
rd
In case the network has predominant 3 order harmonics (150 Hz in 50 Hz networks), the use of detuned filters tuned
at 134 Hz is more common (over voltage factor of p = 14%).
However, a large majority of installations require capacitor bank fitted with detuned filters appropriate for 5th order
harmonics (250 Hz in 50 Hz networks) or higher, which are normally produced by the more usual harmonic current
sources, such as, drives, AC/DC rectifiers, induction ovens, etc. In such cases, there are two options available, that
corresponding to an over voltage factor of p = 7% (tuning frequency of 189 Hz in 50 Hz networks) and p = 5.67%
(tuning frequency of 210 Hz in 50 Hz networks).
It may seem from the above that the choice of a value of p = 7% or p = 5.67% might be indifferent and that both
should give the same result when they are connected to the electrical network, but this is not strictly true.

Detuned Filters and Their Effect on Installations

To follow the arguments of this, we will briefly go through the operating principle of detuned filters.
Impedances ohm

100 115 130 145 160 175 190 205 220 235 250 265 280 295 310

Frequency Hz

7% 5.67%

Fig. 1 Impedance-frequency graph of a detuned filter with p = 7% (189 Hz) and p = 5.67% (210 Hz)

Observing the impedance-frequency graph at rated current of a standard reactor-capacitor unit with p = 7% (green
line in Fig. 1), we see that it offers least impedance at 189 Hz, whereas that corresponding to p = 5.67% (red line in
Fig. 1) offers the least impedance at 210 Hz. In both cases, the impedance gradually increases on either side of it. The
impedance is capacitive at frequencies under 189 Hz for 7% and 210 Hz for 5.67% respectively, and inductive at
higher frequencies. It is this inductive character with harmonic frequencies of the 5th order or higher that prevents
the possibility of a resonance phenomenon being produced at any of those frequencies. However, another key
parameter for the correct operation of the detuned filter is the value of impedance at the different harmonic
frequencies. Therefore, at said impedance-frequency in Fig. 1 the impedance difference of each tuning can clearly be
seen at a harmonic frequency of 250 Hz.
41
What is The Main consequence of difference in Impedance Difference Shown By Both
Tunings?
For p = 5.67%, the value of the impedance is around half of the value for p = 7%. Hence its ability to filter of 5th
Harmonic and above is only half that of a 7% detuned filter.
The result will be that the absorption of harmonic currents by the capacitor will be higher for p = 5.67% than for p =
7% as it is providing less impedance to the harmonic frequency.

Other Effects on The Filtering Tuning

One basic point is the fact that if, to start with, a reactor with p = 5.67% is going to have a larger harmonic current
consumption, then the reactor and the associated capacitor, must be designed to withstand the overload to which
they are to be subjected on the level of intensity and temperature. However, in the particular case of a similarly-
designed reactor with p = 7%, the result is a smaller and lighter reactor, and a lower cost.
In short, in case of reactor with p=5.67%, there is a risk that the capacitor bank might have to withstand higher levels
of harmonic overloading, which would inevitably cause faster wear than in case of a capacitor with filter of p = 7%.
The other essential point to be considered, which is the most important, is the influence of the capacitor capacity in
tuning the reactor-capacitor series group according to the formula for tuning frequency:

1
¦
res =
2pLC

A decrease in the capacitor capacity will result in an increase in the unit's resonance frequency. Capacitors are
elements that lose capacity with time either due to their conditions of use (voltage, temperature, connection
operation rate, etc.), or due to the natural deterioration of the polypropylene of their dielectrics. A same loss of
capacity in a p = 5.67% filter and in one of p = 7% , means that the first will come much closer to the 5th order
frequency than the second, and the closer it comes, the greater harmonic current absorption it will present, the
greater overloading it will suffer, leading to greater deterioration.
In other words, the safety margin given with this loss of capacity is considerably higher in a filter with p = 7%

Conclusions for The Correct Choice of A Reactor

The conclusion in this case is clear, and is the unequivocal recommendation of the use of filters with p = 7% instead
of p = 5.67% in all installations where they have to be applied due to the level of harmonic distortion.
The purpose of this recommendation is none other than to reduce the obvious risk that a loss of capacitor capacity
could cause as a result of overcurrent in the capacitor bank much earlier. Thus, 7% detuned reactors allow a longer
reaction time through pertinent maintenance actions and the application of corrective measures before the damage
is definitive and, therefore, avert worse economic conditions.
 LINEARITY OF REACTOR 42
An industry whose load includes a high proportion of non-linear load (harmonic generating loads), with poor power
factor, requires capacitor with de-tuned filter. This performs the function of power factor improvement while
preventing harmonic amplification.
Ln

- Tolerance
x 1,05
Air Core
x 1,00 Normally, the inductance of the series reactor (of de-tuned filter)
x 0,95 connected is chosen such that the tuning frequency of the de-
tuned filter is 10% below the lowest harmonic frequency with
Iron Core
1,8
considerable current/voltage amplitude. Therefore, resonance
does not happen in the system and reactor offers high
impedance for higher frequency harmonics.
0 1 2 3 Xin

Relation between inductance (LN)

and inductor current (IN)

Normally, 7% detuned reactors are designed considering typical industrial loads such as drives that have the
following harmonic voltages: V3= 0.5% VN, V5= 6% VN, V7= 5% VN and so on. However, if the individual harmonic
voltages increase, the following phenomenon happens:

The magnitude of net current

(through LC) increases

If the current increases beyond certain limit,

the reactor may be driven into its saturation region

Once the reactor saturates, inductance value

(L, in henry) of the reactor starts decreasing
(as L = Nf /I)

Therefore, the resonant frequency (fR) of the LC rises

as resonant frequency = 1 / 2pLC
The new resonant frequency may match the fifth harmonic
frequency and may result in resonance

As the resonant frequency rises, the capacitor-reactor combination

may offer lower impedance to the fifth harmonic component and
the current through the combination may increase further

Thus the resonant frequency of the reactor capacitor

combination may increase continuously resulting in a
thermal runaway

Normally, reactors are designed with predefined linearity. A reactor having a higher linearity does not saturate for
higher harmonic currents and prevents the system from a thermal run away as described above.
43 Q-FACTOR OF REACTOR
The quality factor or Q-factor is a dimensionless parameter that characterizes a resonator's bandwidth relative to its
center frequency. It also describes the damping nature of a resonant circuit. Higher Q indicates a lower rate of energy
loss relative to the stored energy of the oscillator; i.e., the oscillations die out more slowly. For example, a pendulum
suspended from a high-quality bearing, oscillating in air, has a high Q, while a pendulum immersed in oil has a low one.
Oscillators with high quality factors have low damping making them ring longer.

The Q-factor is the ratio of the reactance to the resistance in the circuit. In other words, it is the absolute value of the
ratio of reactive power to real power
~
Z=R+jX

Q= X
R
Thus, we can also calculate the Q-factor, just by knowing the power factor of the circuit

sinf1 - PF2 1
Q= = = -2 -1
cosf PF PF

or just the tangent of the phase angle

Q = tanf
While selecting a detuned filter, it is important to give due consideration to its band-width. The bandwidth will decide
the extent of impendence the filter offers to higher order harmonics. The bandwidth of the filter is a function of the
resistance of the system. The resistance largely depends upon material and construction of the filter inductor.

Bandwidth = F2 -F1 = Fr /Q

Where, F2 is the upper cut off frequency

F1 is the lower cut off frequency and
Fr is the resonant frequency

I0

R1
(High Q Factor)

R2>R1
(Low Q Factor)

R2

Frequency

For an electrically resonant system, the Q-factor represents the effect of electrical resistance, as shown in the figure.
When resistance is low (R1), the system will have a low bandwidth. When the resistance is increased gradually
(say to R2), its bandwidth increases. Thus while selecting De-tuning reactors, care should be taken that the Q factor of
the same is adequate.
 REACTORS - HARMONIC FILTERS 44

The increasing use of modern power electronic apparatus (drives,

uninterruptible power supplies, etc) produces nonlinear current and
thus influences and loads the network with harmonics (line pollution).
The capacitance of the power capacitor forms a resonant circuit in
conjunction with the feeding transformer. Experience shows that the
self-resonant frequency of this circuit is typically between 250 and
500 Hz, i.e. in the region of the 5th and 7th harmonics. Such a
resonance can lead to the following undesirable effects:
n Overloading of capacitors
n Overloading of transformers and transmission equipment
n Interference with metering and control systems, computers and electrical gear
n Resonance elevation, i.e. amplification of harmonics
n Voltage distortion
These resonance phenomena can be avoided by connecting capacitors in series with filter reactors in the PFC system.
These so called “detuned” PFC systems are scaled in a way that the self-resonant frequency is below the lowest line
harmonic and the detuned PFC system is purely inductive as seen by harmonics above this frequency. For the base line
frequency (50 or 60 Hz usually), the detuned system on the other hand acts purely capacitive, thus correcting the reactive
power.

Features
Copper and Aluminium wound
n Reactor Tuning Application
Tuning Factor Frequency Typical Loads
(Harmonic Orders)
reactors
Very low operating losses -
n
5th harmonic (250 Hz)
6 pulse drives (AC / DC),
3 to 5 W / kVAr 7% 189 Hz 3 phase UPS, frequency
and above
converters
High linearity - 1.8 times the
n

rated current 3rd harmonic (150 Hz) Single phase UPS, CFL
14% 133 Hz
Low noise
n and above lamps, SMPS, dimmers
Auto-thermal cutoff**
n

Technical Details (Copper and Aluminium)

Standards IEC 60289, IS 5553
Rated Voltage (V) 440 V
Rated Frequency (F) 50 Hz
Max Permissible Operating Voltage 1.05 Un Continuously, 1.1 Un for 8 hours
Max Permissible Operating Current (Linearity) 1.8 In Continuously
Duty Cycle 100%
Class of Protection I
Ambient Temperature 40oC
Winding Cu / Al
Insulation Class Class H
Protection Thermal Switch (NC contact)**
De-Tuning 5.67%, 7% & 14%

V3 = 0.5% VR (duty cycle = 100%)

V5 = 6.0% VR (duty cycle = 100%)
Harmonics Limit V7 = 5.0% VR (duty cycle = 100%)
V11 = 3.5% VR (duty cycle = 100%)
V13 = 3.0% VR (duty cycle = 100%)

o
** To be connected in series with contactor coil. When temperature exceeds 130 C, NC opens and disconnects the reactor from the circuit.
45
7% & 14% Detuned Reactor (Copper) 440 V - Overall Dimensions

w
L
connect well
terminal type
cmst 2.5 mm sq. / 400 V
(Thermistor - NC contact)

d1
H

d2

n2
d2
d1 n1 n2
Open Slot n1
b
d1 X d2 - 4 Nos. Mounting Plan
Elevation R. H. Side View

Terminal L W H n1 n2
Rated I rms Inductance b d1 d2 Weight
Hole
kVAr Cat. No. Current
(A) (A) (mH) (kg)
All Dimensions in mm

5 LTFR0705B2 6.6 7.5 9.280 6Ø 175 96 ± 5 157 100 55 ± 3 73 10.5 18 7

10 LTFR0710B2 13.12 14.9 4.641 6Ø 178 125 ± 5 161 100 75 ± 3 93 10.5 20 9

12.5 LTFR0712B2 16.5 18.7 3.71 6Ø 178 125 ± 5 161 100 75 ± 3 93 10.5 20 9

15 LTFR0715B2 19.8 22.35 3.1 8Ø 225 150 ± 5 230 150 73 ± 3 93 10.6 21.5 13

20 LTFR0720B2 26.4 29.8 2.328 8Ø 226 152 ± 5 205 150 96 ± 3 109 10.8 22 17

25 LTFR0725B2 32.8 37.2 1.86 8Ø 226 152 ± 5 205 150 96 ± 3 109 10.8 22 18

50 LTFR0750B2 65.61 74.45 0.93 8Ø 260 207 ± 5 240 150 167 ± 3 185 10.6 55 27

75* LTFR0775B2 99 129 0.62 6Ø 300 200 ± 5 265 150 151 ± 3 181 12 20 38

100* LTFR0700B2 131.2 171 0.464 6Ø 330 225 ± 5 300 240 160 ± 3 95 12 20 42

5* LTFR1405B2 6.6 9 20.06 6Ø 210 165±3 180 120 103±3 130±3 12 20 12

10* LTFR1410B2 13.2 17 9.28 6Ø 240 150±3 230 120 93±3 123±3 12 20 17

12.5* LTFR1412B2 16.5 21 8.02 6Ø 240 165±3 230 120 103±3 130±3 12 20 19

15* LTFR1415B2 19.8 26 6.42 6Ø 200 170±3 230 120 113±3 143±3 12 20 23

20* LTFR1420B2 26.4 34 4.64 6Ø 250 155±3 265 150 90±3 126±3 12 20 27

25* LTFR1425B2 32.8 43 4.012 6Ø 300 190±3 265 150 113±3 143±3 12 20 32

50* LTFR1450B2 66 86 2.006 8Ø 275 200±3 285 240 156±3 186±3 12 20 53

75* LTFR1475B2 99 129 1.23 8Ø 330 230±3 295 240 186±3 216±3 12 20 69

100* LTFR1400B2 131.2 171 0.92 10Ø 400 250±3 420 200 165±3 210±3 12 20 110

*Refer to the next page for drawings

 46
7% & 14% Detuned Reactor (Aluminium) 440 V - Overall Dimensions

Thermistor-NC Contact
W
Hole Ø Earthing Bolt

d1

d2

n2
H
n1
Mounting Plan

n1 Open Slot n2
L d1 X d2 - 4 Nos. b

Elevation R. H. Side View

Terminal L H W n1 n2 b d1 d2
Rated I rms Inductance Hole Weight
kVAr Cat. No. Current
(A) (A) (mh) (kg)
All Dimensions in mm

5 LTAL0705B2 6.6 9 9.28 6Ø 215 185 130 ± 3 203 80 ± 3 100 ± 3 8 12 7

10 LTAL0710B2 13.2 18 4.64 6Ø 215 185 155 ± 3 203 92 ± 3 110 ± 3 8 12 9

12.5 LTAL0712B2 16.5 21 3.97 6Ø 215 185 170 ± 3 203 105 ± 3 123 ± 3 8 12 11

15 LTAL0715B2 19.8 26 3.21 6Ø 215 185 196 ± 3 203 130 ± 3 150 ± 3 8 12 14

20 LTAL0720B2 26.4 35 2.32 6Ø 250 225 170 ± 3 150 110 ± 3 140 ± 3 12 20 18

25 LTAL0725B2 33 43 1.85 6Ø 270 265 165 ± 3 150 110 ± 3 140 ± 3 12 20 21

50 LTAL0750B2 66 86 0.92 10Ø 270 375 210 ± 5 150 110 ± 5 140 ± 5 12 20 32

75 LTAL0775B2 99 129 0.62 10Ø 270 385 210 ± 5 150 110 ± 5 140 ± 5 12 20 49

100 LTAL0700B2 132 172 0.46 10Ø 370 305 205 ± 5 180 145 ± 5 185 ± 5 12 20 48

5 LTAL1405B2 6.6 9 20.06 6Ø 215 180 150±3 200 90±3 110±3 12 20 10

10 LTAL1410B2 13.2 17 10.03 6Ø 250 230 160±3 150 105±3 140±3 12 20 18

12.5 LTAL1412B2 16.5 21 8.024 6Ø 250 220 160±3 150 105±3 140±3 12 20 13

15 LTAL1415B2 19.8 26 6.68 6Ø 270 280 180±3 150 125±3 155±3 12 20 26

20 LTAL1420B2 26.4 34 5.015 6Ø 270 280 180±3 150 125±3 155±3 12 20 31

25 LTAL1425B2 32.8 43 4.012 6Ø 270 345 170±3 150 105±3 138±3 12 20 37

50 LTAL1450B2 66 86 2.006 10Ø 370 300 210±3 180 130±3 175±3 12 20 47

75 LTAL1475B2 99 129 1.23 10Ø 370 305 250±3 180 170±3 200±3 12 20 68

100 LTAL1400B2 131.2 171 1.003 10Ø 360 380 250±3 200 170±3 210±3 12 20 82
47 BASICS OF ACTIVE HARMONIC FILTER
The increasing use of energy saving power electronics based loads (adjustable speed drives, switch mode power
supplies, etc.) to improve system efficiency and controllability, is increasing the concern for harmonic distortion levels
in end use facilities and on the overall power system. Active filter is the apt device for reducing harmonic levels in
industrial and commercial facilities to meet IEEE 519 guidelines. The concept of active filter, what many try to explain
is, it senses harmonics and generates 180° phase shifted harmonics that cancels out the unwanted harmonics. This
article, specifically describes the basic operation of active filters in a little more detailed way.

Principle of Operation
An active harmonic filter is based on the following principle:
IFILTER = IMAIN – ILOAD
It detects the difference between the ideal current sine wave (IMAIN) and the actual current which has been deformed
by harmonics (ILOAD). It, then, injects this difference (IFILTER), which is the negative of the harmonic currents present in the
load current, into the system on a real-time basis. This cancels out the high frequency harmonics and results in almost
pure sine wave.

Load Current Sinusoidal Supply

with harmonics Supply Current System

IMAIN
Compensating
current

ILOAD Active
Filter

IFILTER

100ms 110ms 120ms 130ms 140ms (Time Domain)

Wave Shapes of The Currents - IMAIN, ILOAD & IFILTER

(Frequency Domain)

Line Diagram of Active Harmonic Filter

The use of active harmonic filters helps in reducing harmonics as can been seen under:

Before AHF After AHF

100 100

80 80
Amplitude (%)

Amplitude (%)

60 60

40 40

20 20

0 0
1 3 5 7 9 11 13 15 17 19 21 1 3 5 7 9 11 13 15 17 19 21
Harmonics order Harmonics order

Frequency Spectrum of Current Before and After Active Harmonic Filtering

 48
Some of the areas where active harmonic filters can be used are:
• In areas with critical loads like automobile industry, precision equipment manufacturing etc., the harmonic
load may vary frequently. This may have immediate adverse impacts like poor quality of manufactured
products and equipment failures leading to huge monetary losses. Active filters prove to be suitable as they
provide real-time reduction of THD
• Certain segments like textile industry, having huge VFD loads suffer from high harmonics. Due to this, the
use of detuned filters may not be adequate, resulting in frequent capacitor failures and overheating or
saturation of reactors. Only active harmonic filters provide necessary solutions in such cases
• Active harmonic filters have an added advantage of providing unsymmetrical reactive power compensation
and also, provide load balancing
• Even usage of 14% reactor may not be sufficient to reduce neutral overloading due to triple-N harmonics.
However, 3 phase, 4 wire active filter helps in achieving the same more effectively

Active Harmonic Filters - Concepts & Connections

The active filter uses power electronic switching to generate harmonic currents that cancel the harmonic currents
from a nonlinear load. The active filter configuration is based on a Pulse-Width Modulated (PWM**) voltage source
inverter that interfaces to the system through an Interface Filter as shown in Figure 1. In this configuration, the filter is
connected in parallel with the load being compensated. Therefore, the active filter with this configuration is often
referred to as shunt active filter. Figure 1 illustrates the concept of the harmonic current cancellation so that the
current being supplied from the source is sinusoidal.

IS IL
M
If
Nonlinear
Main Customer Load
Bus

Interface Filter

IGBT Controls
PWM and
Inverter Gate Signal
Generation

Figure 1

**Pulse Width Modulation is a technique used to generate the effect of any wave-form by varying the width of the DC pulse. The width (duty
cycle) is varied by employing faster switching devices (IGBT with switching frequency in kHz). Higher the switching frequency, better will be the
intended wave-form but higher will be the power losses.

The voltage source inverter used in the active filter makes the harmonic control possible. This inverter uses DC
capacitors as the supply and can switch at a high frequency to generate a signal which will cancel the harmonics from
the nonlinear load. One leg of the inverter is shown in Figure 2 to illustrate the configuration.

IGBT
DC Cap.

L1f L2f
Diode
Neutral

Source
Cf

Figure 2
49
The current waveform for cancelling harmonics is achieved with the voltage source inverter and an interfacing filter.
The filter consists of a relatively large isolation inductance to convert the voltage signal created by the inverter to a
current signal for cancelling harmonics. The rest of the filter provides smoothing and isolation for high frequency
components. The desired current waveform is obtained by accurately controlling the switching of the IGBTs in the
inverter. Control of the current wave shape is limited by the switching frequency of the inverter and by the available
driving voltage across the interfacing inductance.
The active filter does not need to provide any real power to cancel harmonic currents from the load. The harmonic
currents to be cancelled show up as reactive power.

Connections & CT installations of Active Harmonic Filters

For the stable operation of active harmonic filter and for the expected reduction of harmonics, the physical
connection & location of power cables & CTs plays a critical role. Let us understand the connections through the
below two cases.
Case 1: In case any industry faces severe problems due to harmonics like over-heating of equipments, failure of
power capacitors, frequent card failures, etc., it is advisable to arrest the harmonics right at the source. The
connection shall be as below:

CT

PCC

CT

MCC

Linear loads Detuned APFC

AHF Non-linear load

Make sure that the APFC panels are detuned and are connected in the upstream of the AHF. Detuning of APFC panel
helps in optimising the AHF rating, as detuning avoids the harmonic amplification. Connecting AHF below the APFC
avoids the AHF being overloaded due to unwanted harmonic resonances. Also make sure that the CT of AHF shall be
connected below the CT of APFC panel.
Case 2: If almost all the main feeders from PCC generates high harmonics, ideally each feeder shall be compensated
with individual AHF. But this will increase the installation cost and requires more space. Also managing all the AHF
will be difficult. In such cases, a common AHF can be connected for harmonics compensation, as shown below:

CT

AHF Non-linear load Linear Detuned

loads APFC

Also make sure that the APFC panels are detuned and the AHF CT shall be below the CT of detuned APFC panels. This
method is also simple enough, especially for industries where harmonics need to be reduced at the HT side, in order
to meet utility regulations (like Tamil Nadu Electricity Board).
In some rare cases, there may be multiple sources, like two or more synchronised transformers. In such cases,
individual CTs shall be connected to each sources and the common signal can be given to AHF through a summation
CT.
 50
Open loop connection Vs closed loop connection
The open loop or closed loop connection is indicated by the location, where harmonics are measured by the AHF. In
simple words, CT position states whether the connection is open loop or closed loop connection.

In open loop connection, CT is installed close to load, as indicated in

the above figure. AHF senses the harmonics that are being generated
Load
by the load and generates the compensating harmonics based on Source CT
that data. Advantage of this connection is faster harmonic
compensation. But a drawback in this connection is, the AHF won't
get any feedback from the system and does not know whether the
harmonics compensation is happening properly or not. Also, as no
feedback exists, the resulting line current may typically contain error AHF
components that are not detected by the control system. This
Open Loop Connection
connection works better when AHF is connected close to the load and
not at PCC / main incomer.

In closed loop connection the CT is installed close to source. Here,

Load CT actually measures the compensated current. In other words, AHF
Source CT senses the difference between load current and the AHF
compensating current. If CT senses any harmonics, corrective action
is taken by the AHF, till CT senses close to sine wave. In this method of
connection, the AHF gets system feedback and any measurement or
AHF
other inaccuracies can be automatically cancelled out. Even though,
closed loop connection is not as fast as open loop, closed loop
Closed Loop Connection ensures better harmonics compensation. This type of connection
works better, anywhere in the system, than the open loop.

Selection / Sizing of Nominal Current of Active Harmonic Filter

Active harmonic filter is rated in Amperes. The current rating is decided on the basis of harmonic content (THD) in the
system which can be obtained from harmonic study. The required nominal current can be obtained by multiplying the
initial current of harmonics measured in the load by a safety factor (SFh) of 20%. In other words,

Ifilter (AHF) = 1.2 x Iload x %THD (I)

Where,
Ifilter (AHF) : Nominal Current of Active Filter (A)
Iload : Maximum Load Current (A)
% THD(I) : Load Current Harmonic Distortion (%)

Majority of the energy saving devices are non-linear in nature. Consequently, the problem of harmonics has become
inevitable. Advanced devices like active harmonic filter provide an ideal solution to this problem. These filters help in
maintaining a stable and healthy power system thereby increasing productivity and efficiency.
51 ACTIVE HARMONIC FILTERS
Active Harmonic filters are the most ideal solution for power quality problems caused, in either industrial or
commercial facilities, for harmonic filtering, phase balancing and reactive power compensation.

Without AHF With AHF

Function
THD TOTAL
• Harmonic Filtering:
th LOAD MAINS
The filters reduce harmonics up to the 50 order (2500 Hz)
reducing distortion power factor. Selection of specific L1 21% 5%
harmonic order for filtering helps in optimizing filtering
L2 18% 5%
efficiency.
L3 19% 5%
3 Phase 4 Wire filter configuration ensures reduction in
neutral current that can reach up to 200% of rated value
due to triple-N harmonics. Harmonic Filtering

VOLTAGE & CURRENT

CURRENT • Phase Unbalance Correction:
VOLTAGE LOAD MAINS
This function ensures balanced current on the supply
L1 232 V 199 A 220 A
side in 3 Phase 4 Wire filter configuration.
L2 231 V 206 A 221 A
L3 231 V 255 A 221 A
FREQUENCY 50 Hz

Phase Balancing

• Power Factor Correction: POWER MAINS

This filter ensures close to unity displacement P Q S PF
power factor for both lagging (inductive) and L1 41.6 kW 5.92 kVAr 42.02 kVA 0.99
leading (capacitive) current systems. With
L2 38.9 kW 5.52 kVAr 39.29 kVA 0.99
improvement in both distortion and displacement
L3 48.0 kW 6.80 kVAr 48.48 kVA 0.99
power factor, true power factor is also improved.

Reactive Power Compensation

 52
Features & Benefits

Features Advantages Benefits

Employs floating Point 32 bit

Digital Signal Processor High accuracy & high
Effective harmonic
attenuation up to 96% of mitigation
Programmable selective individual harmonics
harmonic elimination

Any number of units of different Modularity & expandability Reduced Mean Time to Repair;
ratings can be connected in Filter can be expanded as per
parallel future load requirements

Employs high speed IGBTs in Faster response to change in THD can be maintained even
power circuit THD and very high speed in case of very frequently
of operation changing load

Provision of Alarms Easy diagnosis of fault Safety to devices and

conditions operators

7” TFT touch screen HMI Easy configuration and Ease of installation and
parameter monitoring maintenance, User-friendly

Ethernet based communication Remote monitoring Ease of monitoring

Configuration in both open loop Faster response & higher Flexibility of configuration
(load side sensing) and closed attenuation of harmonics
loop (source side sensing)

The active filter is ideal in any application that has a large variation of loads, a wide
spectrum of harmonics that must be compensated. Non-linear loads that are heavily
distributed in the form of small network loads, so that it is not possible to use
individual passive filters.

The most common applications are:

• Variable frequency drives
• Computer loads
• UPS
• CFL Lamps

In other words, its application is in any industry where large non-linear loads are present with high THD.
Such high THD are prevalent in the following industries:

• Automotive Industry • Textile Industry • Cement Industry

• Data Centres • Paper Mills • Oil & Gas Exploration

• Wind Turbines • Sugar Plants • Water Treatment

• Building & Infrastructure • Pharmaceutical Industry • Granite & Stone Polishing
53
Connection Diagram
LOAD SIDE MAINS SIDE LOAD SIDE MAINS SIDE
L1 L1
L2 L2
L3 L3
N N

L1 L2 L3 N L1 L2 L3 N

Active Filter Active Filter

Close Loop Connection Open Loop Connection

Technical Specifications
INPUT
Model AHF - 4W/3W
Normal Voltage 400V AC ±10%, 3Ph 4 Wire/3 Wire (690V optional)
Current Rating 30A 60A 75A 150A 100A 200A 300A 400A 600A
Frequency 50Hz,+/-5%
FILTER
Harmonic Range nd th
2 to 50 order
Harmonic Selection Any 20 Harmonic can be selected at a time
Harmonic Attenuation Ratio Up to 96% at rated current
Response Time <1 ms
Function Selection Harmonic filtering, Power factor correction, Load balancing
Overload (peak value) 125% for 10 msec
30A 60A 75A 150A 100A 200A 300A 400A 600A
Current Transformer 500A:5A 1000A:5A 3000A:5A 5000A:5A 6000A:5A
Class 1, 15VA rating
PHYSICAL CHARACTERISTICS
Protection Class IP20 (IP31 or IP41 optional)
Cooling Forced air
Cable Entry Front - Bottom
ENVIRONMENTAL
Operating Temperature 0 to 40 C
O

Relative Humidity 95% (Non condensing)

Maximum Operating Altitude
without De-rating 1000 m

Acoustic Noise at 1m From

Panel Front (Ref ISO3746) < 65 db < 68 db < 70 db

USER INTERFACE
User Parameter Setting LCD touch screen HMI
PROTECTIONS AND STANDARDS
Protections MCCB & fast acting semiconductor fuses
DC over voltage, Over load trip, Over temperature alarm & trip, Over current,
Alarms No synchronisation, Mains abnormal, DC under voltage, Active filter trip, Wrong phase,
No faults, Fast DC overvoltage, Inductor over temperature trip
Reference Design Standard IEC 60146
Safety Standard EN 50178
EN 55011, IEC EN 50081-2, IEC 61000-4-2, IEC 61000-4-3,
Electromagnetic Compatibility
IEC 61000-4-4, IEC 61000-4-5, IEC 610004-6, IEC 61000-6-2
 54
Overall Dimensions

AHF - 3W/4W 30/60/75/100

3 Ph 3 Wire / 4 Wire, 400 V Active Filter

Cable size- Dimensions (mm)

Cat. No. Model No. Copper
single core Weight
flexible (kg) Width Depth Height Plinth

AHF030331D2 AHF - 3W- 30A 4x10 sq.mm 45 Wall-

Height
Height

550 300 800 Mounting

AHF030341D2 AHF - 4W - 30A 6x25 sq.mm 48

AHF060331D2 AHF - 3W- 60A 4x25 sq.mm 65

620 450 1000 100
AHF060341D2 AHF - 4W - 60A 6x25 sq.mm 70

AHF075331D2 AHF - 3W- 75A 4x35 sq.mm 75

620 450 1000 100
AHF075341D2 AHF - 4W - 75A 6x35 sq.mm 80
Plinth

Plinth

AHF100331D2 AHF - 3W- 100A 4x50 sq.mm 85

620 450 1000 100
Width Depth AHF100341D2 AHF - 4W - 100A 6x50 sq.mm 90

Front View Side View

AHF - 3W/4W 150/200/300/400/600

3 Ph 3 Wire / 4 Wire, 400 V Active Filter

Dimensions (mm)
Cable size-
Cat. No. Model No. Copper single Weight
core flexible Width Depth Height Plinth
(kg)

AHF150331D2 AHF - 3W- 150A 4x70 sq.mm 175

800 850 1600 150
AHF150341D2 AHF - 4W- 150A 6x70 sq.mm 205
Height
Height

AHF200331D2 AHF - 3W- 200A 4x70 sq.mm 225

800 850 1600 150
AHF200341D2 AHF - 4W - 200A 6x70 sq.mm 265
AHF300331D2 AHF - 3W- 300A 4x120 sq.mm 310
800 850 1600 150
AHF300341D2 AHF - 4W - 300A 6x120 sq.mm 365
AHF400331D2 AHF - 3W- 400A 4x(2x70) sq.mm 430 1000 900 1600 150
AHF600331D2 AHF - 3W- 600A 4x(2x120) sq.mm 600 1000 900 1600 150
Plinth
Plinth

Width Depth

Front view Side view

 HARMONICS AND ITS IMPACTS ON POWER FACTOR -
55 DISTORTION POWER FACTOR
Defining Power Factor
Power factor is usually identified as the cosine of angle between the voltage sine wave and the current sine wave. For
a better understanding, it can be seen as the efficiency of electricity consumption. Similar to the efficiency of a
machine, it can be defined as the ratio of output power rendered by the machine to the machine input power. Hence,
it is the ratio of True power (kW) to Apparent Power (kVA).
kW
Power factor (PF) =
kVA
However, it is not the only power factor present in the system. Depending on which value of voltage and current we
consider, there are different types of power factors:
• Displacement PF
• Distortion PF
• True PF

Types of Power Factor

1. Displacement PF – The power factor which is due to the phase shift between voltage and current at the
fundamental frequency is known as distortion power factor.
P
Displacement PF =
V1I1
2. Distortion PF – The power factor which includes the effect of harmonics present in the system is called distortion
power factor.

Distortion PF =
1
1+%iTHD2

3. True PF – It is defined as the ratio of average power to apparent power.

Both the above power factors together combine to form the True power factor.

True PF = Displacement PF x Distortion PF

P
Distortion PF =
Vrms I rms

Different types, different implications

Understanding the various types of power factor is very important because all three have different implications.
When we talk about power factor correction by means of capacitors, we are referring to improvement of only the
displacement power factor, which consequently improves the true power factor. Capacitors act like an alternate
“source” of reactive power and hence by decreasing the “inductiveness” of the system, they reduce the lag between
the current and voltage phase, thus improving the power factor. But it is important to note that these voltage and
current waves are with respect to the fundamental component i.e. 50 Hz. There might be some cases where even
after installing capacitors at site, the power factor doesn't improve.
Here distortion power factor comes into picture.
Under normal load conditions,

kVA = kW
PF
Here, the system current is the rms current at 50 Hz.
For pure sinusoidal cases (systems without Harmonics),

PF true = PF disp = cos f

where f is the angle between voltage and current wave

In case of a system with Non Linear loads, when the system is polluted by harmonics, the rms current increases as
seen by the following formula –
2
I = I1 1 + iTHD
 56
Increase in rms current consequently leads to increase in kVA demand. But the kW output of the system would
remain the same.

kW
Following the formula kVA = ,
PF
If kVA demand increases with kW remaining constant, power factor has to decrease. This decrease in power factor
due to the presence of harmonics can be attributed to the 'distortion power factor'. Here true power factor becomes
a product of displacement and distortion power factor. Hence, even if the displacement PF is corrected up to unity,
the true PF will still remain low because of poor distortion PF.
Mathematically, distortion PF can be calculated as :

1 I1
PFdist = =
2 Irms
1+ iTHD
where I1 is the rms value of the fundamental current and Irms is the rms value of total current.
Harmonic levels are measured as Total Harmonic Distortion (THD). Higher THD implies lower distortion PF. The graph
below depicts the impact of THD levels on the true power factor of non linear loads.

0.9
Maximum Time
Power Factor

08

07

0.6

0.5
0 20 40 60 80 100 120 140

THD of Current

The following table shows how different types of power factor vary with THD.
Displacement PF
THD-I (assumed to be compensated Distortion PF True PF
by equivalent Capacitors)
5% 0.999 0.999 0.998
30% 0.999 0.958 0.957
40% 0.999 0.929 0.928

Capacitors don't do any good in correcting distortion power factor. In harmonic rich environment, using capacitors
can even be detrimental to the installation as it can lead to harmonic resonance and harmonic amplification. Hence,
in such cases, we need to use detuned reactors along with capacitors to avoid amplification.
APFC panels with detuned filters can effectively increase the displacement pf to unity. But the distortion pf will still
remain low due to the presence of harmonics in the system. And hence, the true power factor will remain low, as
seen in the above table. Thus, to improve distortion PF, Active Harmonic Filter should be used to mitigate harmonics.

The smart choice

For improving true power factor, correction of both displacement and distortion power factor is required. Capacitors
are the means for improving solely the displacement power factor. But we can't overlook the repercussions of using
capacitors alone in systems with high harmonics. In a harmonics rich environment, Active Harmonic Filter must be
used to improve distortion PF. Hence, for power factor correction, hybrid filter (capacitor-reactor combination with
AHF) is the smart choice.
 CAPACITOR SWITCHING IN APFC PANEL 58
The switching of capacitor banks is a special and challenging task in Automatic Power Factor Correction (APFC)
panels. The selection of appropriate switching device for such application is based on two criteria:
n Ability to carry rated capacitor current continuously
n Ability to withstand the peak-inrush current of capacitor
It is simple to calculate the capacitor rated current and select the switching device to be able to carry rated capacitor
current (2.5 to 3 times the capacitor rated current to take care of overload, harmonics, supply voltage variation and
capacitor value tolerance). However, it is little difficult to select the switching device which is able to withstand the
peak-inrush current. This is because the peak inrush current for capacitor switching application depends upon
various factors such as:
The inductance of the network (including cables, switchgears and transformer)
n

The transformer power rating and percentage impedance

n

Method used for power factor correction

n

Ø Fixed capacitor bank

Ø Multi-stage capacitor bank with steps of equal ratings
Ø Multi-stage capacitor bank with steps of unequal ratings
In multi-stage capacitor bank, the numbers and rating of steps already switched on
n

In most of the installations, the multi-stage capacitor banks are used as steps of unequal ratings. The bigger steps of
higher kVAr ratings being switched on initially and smaller steps are switched on periodically, for achieving the
targeted power factor. In such cases, the value of inrush-current peak will be far higher and hence the smaller
capacitors will be heavily stressed.

Capacitor switching can be done by various ways like:

Power Contactor
Normal power contactors simply allow the inrush current to flow through it. Because of this, contactors and
n

capacitors are heavily stressed. So the contactor selection should be such that it withstands the heavy inrush
current. Hence, power contactors need to be heavily de-rated.
This inrush current also stresses the power capacitors and may result in their premature failure.
n

Power contactors should be used along with inrush current limiting resistors, for reducing the magnitude of inrush
n

current. However, this increases the cost & size of the APFC panel along with extra power losses.

Capacitor Duty Contactor

Capacitor duty contactors can be used to limit the inrush current to less than 10*IN.
n

Capacitor duty contactors have pre-contacts/auxiliary contacts with current limiting resistors (of 4 W
n ). At the
moment of switching, the pre-contacts (with resistors) close first. This reduces the inrush current to less than 10*IN.
After a few milliseconds, main contacts are closed and the pre-contacts will open and go out of the circuit.
Capacitor duty contactors are employed where the frequency of switching is less i.e., the load fluctuation is not
n

very fast. The capacitor requires atleast 60 seconds to discharge to a nominal value (50 V). So capacitor duty
contactors cannot be used when load fluctuation is heavy.

Thyristor Switching Module (TSM)

TSM is a static switching device that is used specially for switching capacitors (dynamic power factor correction),
n

wherever the load fluctuation is heavy (like welding, steel rolling, etc.).
Rapid switching (5 ms to 20 ms) is possible with TSM along with Quick Discharge Resistor (QDR).
n

There is no inrush current while using TSM (zero voltage switching). So frequent switching does not affect the life
n

of capacitors and there is no need for extra current limiting resistors.

TSM has thermal cutoff, which switches off the module when temperature exceeds beyond a certain limit. It
n

automatically switches on when optimum temperature is attained.

59 CAPACITOR DUTY CONTACTORS - TYPE MO C
MO C Capacitor Duty Contactors are specially designed for capacitor switching
applications. As capacitor switching is associated with high inrush current, the
contactors are provided with damping resistors which limit the value of inrush
current to a safe value. The contactors are used in APFC panels for switching power
capacitors depending upon the amount of reactive power compensation required.

Benefits of using Capacitor Duty Contactors

Since switching of capacitor banks involves high transient inrush currents, the size
of the contactor required to switch these high currents becomes higher. Hence,
current limiting inductors are used in series to attenuate this inrush current. This
increases the system cost and panel space.
A typical case below illustrates the magnitude of transient inrush current for
switching of a capacitor bank. For a 12.5 kVAr capacitor bank:

Rated current of 12.5 kVAr 415 V Capacitor = 18A

Peak Inrush current without Damping Resistors = 1200A

Capacitor Duty Contactors are designed to limit this high transient inrush current by introducing damping resistors
with early make auxiliary contacts. The current limiting due to damping resistors protects the APFC system from
harmful effects of the capacitor charging inrush current.

Peak Inrush current with Damping Resistors = 260A

It is observed that peak inrush current with damping resistors is one fifth of that without damping resistors. As the
contactor is now required to switch the rated capacitor current, the size of the contactor required is smaller. Thus the
system cost and panel space are significantly lower when Capacitor Duty Contactors are used.

MO C Capacitor Duty Contactors

MO C Capacitor Duty Contactors are designed for switching 3 phase, single or multi-step capacitor bank. In
conventional capacitor switching contactors, early make auxiliary contacts used for insertion of damping resistors
used to remain in the circuit continuously. During current breaking these auxiliary contacts would also carry and
break the currents due to higher arc resistance in the main pole during arcing. This current breaking by auxiliary
contacts at higher transient recovery voltage causes unreliable product performance and premature product failures.

MO C range of capacitor switching contactors have patented mechanism which disconnects the early make auxiliary
contacts after the main contacts are closed. This completely eliminates the possibility of auxiliary contacts carrying
and breaking the currents during breaking operation. This enhances the product switching performance and
improves the product life.

Features and Benefits of MO C Capacitor Duty Contactors

Feature Customer Benefits
Improved switching performance
De-latching auxiliary contacts
Reduced losses in auxiliary contacts
Dual contact gap for auxiliary contacts
Higher electrical life
Enhanced product safety
Encapsulated resistor assembly
No flash over between phases
Ease of wiring
Separate termination of damping resistors
Enhanced operational reliability
Improved switching performance
Wide and chatter-free operating band
Higher electrical life
and in-built surge suppressor
Higher product reliability
 60
Ordering Information
Contactors
Product Designation kVAr Rating @ 415V 50Hz In Built Aux contacts Cat. No.*
MO C3 3 1 NO CS96146
MO C5 5 1 NO CS96127
MO C8.5 8.5 1 NO CS96320
MO C10 10 1 NO CS96156
MO C12.5 12.5 1 NO CS96321
MO C15 15 1 NO CS90019
MO C20 20 1 NO CS90021
MO C25 25 1 NO CS96322
MO C30 30 1 NO CS96148
MO C40 40 1 NO CS96147
MO C50 50 1 NO CS96324
MO C60 60 1 NO CS96149
MO C75 75 1 NO CS96150
MO C85 85 1 NO CS90160
MO C100 100 1 NO CS90158

*: Add four digit suffix as per coil voltage

Accessories & Spares

Add on Blocks Spare Coils
Mounting Position Contacts Cat. No. For Contactor Cat. No.
First Left 1 NO + 1 NC CS94580OOOO MO C3 - C30 CS96317
First Right 1 NO + 1 NC CS94581OOOO MO C40 - 60 CS96318
Second Left 1 NO + 1 NC CS94582OOOO MO C70 - 100 CS96319
Second Right 1 NO + 1 NC CS94583OOOO * Add four digit suffix as per coil voltage

MO C Spreader Link Kit

For Contactor Cat. No.
MO C3-30 CS94274OOOO
MO C40-60 CS94093OOOO
MO C75-100 CS94094OOOO

Note: 1) Spreader Link Kit consists of six terminals

2) Use above Spreader Link when using
MO C 25 16 sq. mm cable

Ordering Suffix for Coil Voltages

Std Coil Voltage 110 220 240 415
Ordering Suffix - 50 Hz AOOO KOOO BOOO DOOO
Ordering Suffix - 60 Hz YOOO VOOO - SOOO
61
Technical Specification

• Available for capacitor range from 3 - 100 kVAr

• Modular design saving precious panel space
• De-Latching auxiliary contacts
• Separate termination of damping resistors
• Encapsulated resistor assembly ensuring safety
• In-built surge supressor with the coil
• Lugless termination

Type Designation MO C3 MO C5 MO C8.5 MO C10 MO C12.5

#
kVAr Rating (at System voltage 440 V) kVAr 3 5 9 10 13
Built in
Catalogue No. Aux 1 NO CS96146 CS96127 CS96320 CS96156 CS96321
Contacts
Conformance to Standards

Rated Operational Current at 440 V, 50 Hz Ie A 3.9 6.6 11.2 13.1 16.4

Short Circuit Protection

Max. Operational Voltage Ue V 690 690 690 690 690

Rated insulation Voltage Ui V 1000 1000 1000 1000 1000

Rated Impulse Withstand Voltage Uimp kV 8 8 8 8 8

Degree of Protection

Solid Conductor mm2 2 x 10 2 x 10 2 x 10 2 x 10 2 x 10

Main Terminal 2
Stranded Conductor mm 2 x 10 2 x 10 2 x 10 2 x 10 2 x 10
Capacity
2
Finely Stranded Conductor mm 2x6 2x6 2x6 2x6 2x6

Coil Operating Pick-up % Uc V 65 - 110 65 - 110 65 - 110 65 - 110 65 - 110

Band Drop-off % Uc V 35 - 65 35 - 65 35 - 65 35 - 65 35 - 65

Pick-up VA 77 77 77 77 77
Coil
VA 9 9 9 9 9
Consumption
Hold-on
W 3 3 3 3 3

Mechanical Million 10 10 10 10 10
Life (Operating Cycles)
Electrical Million 0.2 0.2 0.2 0.2 0.2

Max. Operating Frequency Operations / Hr 240 240 240 240 240

Operating Making
Sequence Breaking

Height H mm 87 87 87 87 87

Overall Width W mm 45 45 45 45 45
Dimensions Depth mm 133.5 133.5 133.5 133.5 133.5
D
Mounting Dimensions mm 35 x 60 - 65 - 70 35 x 60 - 65 - 70 35 x 60 - 65 - 70 35 x 60 - 65 - 70 35 x 60 - 65 - 70

Note: Contact replacement is not permitted in MO C contactors

* Accessories and Spares same as that of MO contactor.
** Dimension is with the spreader link
# kVAr ratings should be selected as per the net kVAr of the capacitor reactor combination irrespective of capacitor voltage (440V/480V/525V)
# While selection it should be ensured that current rating of capacitor is less than the current through the contactor
$ Use spreader while using 16 sq.mm cable
$$ Terminal capacity mentioned is with spreader
 62

MO C15 MO C20 MO C25 MO C30 MO C40 MO C50 MO C60 MO C75 MO C85 MO C100

15 20 25 30 40 50 60 75 85 100

CS90019 CS90021 CS96322 CS96148 CS96147 CS96324 CS96149 CS96150 CS96160 CS96158

IS/IEC 60947-4-1, IEC 60947-4-1, EN 60947-4-1

19.7 26.2 32.8 39.4 52.5 65.6 78.7 98.4 111.5 131

gG type fuses rated at 1.5-2 Ie

690 690 690 690 690 690 690 690 690 690

1000 1000 1000 1000 1000 1000 1000 1000 1000 1000

8 8 8 8 8 8 8 8 8 8

IP20
$
2 x 10 2 x 10 2 x 10 2 x16$$ - - - - - -

2 x 10 2 x 10 2 x 10
$
2 x16
$$
2 x 35 2 x 35 2 x 35
$$
2 x 70 2 x 70 2 x 95$$

2x6 2x6 2 x 6$ 2 x16$$ 2 x 35 2 x 25 2 x 35$$ 2 x 50 2 x 50 2 x 95$$

65 - 110 65 - 110 65 - 110 65 - 110 75 - 110 75 - 110 75-110 75 - 110 75 - 110 75 - 110

35 - 65 35 - 65 35 - 65 35 - 65 35 - 65 35 - 65 35 - 65 35 - 65 35 - 65 35 - 65

77 77 77 77 144 144 144 240 240 240

9 9 9 9 15 15 15 25 25 25

3 3 3 3 6 6 6 9 9 9

10 10 10 10 10 10 10 10 10 10

0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2

240 240 240 240 240 240 240 240 240 240

Early Make / Main

Main Contacts Break

87 87 87 115** 123.5 123.5 174** 135 135 195**

45 45 45 56** 55 55 73** 70 70 95**

133.5 133.5 133.5 133.5** 163 163 163** 175 175 175**
35 x 60 - 65 - 70 35 x 60 - 65 - 70 35 x 60 - 65 - 70 35 x 60 - 65 - 70 45x100 - 105 45 x 100 - 105 45x100 - 105 60x115 - 120 60 x115 - 120 60 x115 - 120
63
Technical Details

MO C

2T1 4T2 6T3

D

A
T
L

C H
Mounting
Screw
W

P P
MO C
Label
3 - 30 40 - 60 70 - 100
W 45 55 70
D 133.5 163 175
H 87 123.5 135
N 26 26 26
T 60 68 68
N

C 22.8 27 35
L 19.6 29.5 30
S 50 82 93
P 14.4 18 23
A 113 142 154

All dimensions in mm.

 DYNAMIC POWER FACTOR CORRECTION 64
Conventionally, power factor correction systems consist of power factor correction capacitors switched using
capacitor duty contactors. The re-switching time is the sum of capacitor discharge time (within 75 seconds as per IEC
60831) and response time of contactor. Such arrangement is suitable for applications where few switching
operations take place per day.
Many applications increasingly require real-time reactive compensation. With this, the demand for dynamic power
factor correction arises and faster switching of capacitors becomes inevitable.
This article discusses the need for thyristor switching module and the care to be taken while designing systems with
thyristor switching modules.

Need for Dynamic Power Factor Correction

Faster response is needed when the demand for reactive power is rapidly fluctuating either due to rapidly changing
load conditions or process requirements. For certain loads, like,
• Welding equipment
• Injection moulding equipment
• Industrial presses
• Loads such as, lifting cranes, elevators, lifts etc.
the demand for reactive power comes frequently and for short duration of time.
Large reactive power demand for very short durations has severe ill-effects, such as:
• Rapid fluctuations in voltage which may lead to system instability
• High voltage transients may result in insulation breakdown or damage to other loads
• Malfunctioning of sensitive electrical and electronic equipment such as relays, PLCs
• Oversizing of electrical installation is needed since kVA capacity needs to be provided for maximum power
demand

Why Not Contactors?

Contactors are electro-mechanical devices which switch capacitors after a lag. Also, due to discharge time of
capacitors, the re-switching time of contactors becomes longer than 60 seconds. This makes contactor a slow device.
In-rush current in capacitor switching are reduced to 10 times the rated current if capacitor duty contactors are used.
However, a certain pulse element is inevitable as can be seen in Figure 1.

I= 1200A I= 1260A
IP

IP

t t

Figure 1 : Transient during capacitor switching by a) Normal contactor b) Capacitor-duty contactor

Inrush current occurences cause high eletromechanical forces within the capacitor. The dielectric inside the capacitor
is highly stressed due to this high current. This could lead to reduction in the life of capacitors.
In order to obviate the above shortfalls, the thyristor switching modules are used.

Principle of Operation of TSM

A thyristor switching module (TSM) is a fast, electronically controlled thyristor switch for switching capacitor loads
within a few milliseconds as often and as long as required.
65
First of all, being a thyristor-based switch, the thyristor switches the capacitor without delay. A thyristor switching
module works on the principle of zero-voltage switching, i.e., the capacitor is switched ON only when the voltage
waveform is at its zero crossing. The current through a capacitor is given by:
dVC
IC= C
dt
Where, IC is capacitor current, C is capacitance and VC is voltage across capacitor. This current is directly proportional
to the rate of change of voltage across the capacitor. Thus, when capacitors are switched ON at zero crossing of
supply voltage, the voltage applied to the capacitor is almost zero and grows steadily following the sine wave. Thus,
the inrush current becomes equal to the rated current.

Control signal

Capacitor current

Figure 2 : Zero in-rush current during capacitor switching by TSM

Importance of QDR
Another point to be noted here is that the capacitors used with TSM should be fitted with quick discharge resistors
(QDR). If the capacitors are used with the usual discharge resistors, then, the capacitor may not get fully discharged at
the time of re-switching. In such a situation, there will still be a significant voltage across the capacitor resulting in
high inrush current. Quick discharge resistors ensure that the capacitor is completely discharged before its re-
switching. The typical discharge time of normal resistors is to reach less than 50 V within 60 seconds. However, for
QDR, the discharge time is reduced significantly so that there is a higher probability of switching at zero crossover,
making the capacitors suitable to be used with thyristor switching modules.

L1 L2 L3
PIV Rating of TSM
The typical arrangement of thyristor switches in a thyristor switching
module is given in figure 3. Two terminals of a delta connected-capacitor High Speed Fuse
are connected to the line via TSM while the third is connected directly to
the line (all three phases have high speed fuses for branch protection).
This configuration obviates the need to use three switch-pairs while
ensuring that the three-phase capacitor is connected only when both TSM
switch pairs are ON or the module is ON. Each switches pair is a
combination of two thyristors connected in anti-parallel for operation
with ac voltage.

Peak Inverse Voltage (PIV) rating of a thyristor switch is the maximum

peak voltage that the thyristor can withstand in the reverse biased
condition. It is the maximum voltage that it must block when it is in OFF Capacitor
condition. A module with thyristors of lower PIV, say 1600 V, is likely to
fail in presence high voltage surges. Hence, higher values of PIV are
desirable. Typically, in capacitor switching applications, the PIV ratings
are up to 2200 V.
Figure 3 Arrangement of thyristor in a TSM
 66
Advantages of TSM
• Faster switching of capacitors with response time from 5-40 ms can be achieved.
• No delay due to capacitor discharge
• No inrush current ensures that there are no resulting voltage fluctuations or transients. Thus, we get transient-free
smooth switching and stable voltage and increased life of capacitors.
• No arcing owing to a static switch
• Thyristor switches allow any number of switching operations as they are not subjected to any mechanical wear.
Thus, a longer service life as compared to contactors.
• With dynamic compensation, reactive power is more efficiently compensated resulting in further lowering of
energy costs.
• With reduced peak of inrush current, cables and equipment used can be of smaller short circuit rating reducing
capital expenditure.

High Speed Fuse for Branch Protection

For short circuit protection of a thyristor switching module, a faster protection device is needed so that it will act
before the thyristor switch in case of a short circuit. Normally, an HRC fuse has a time characteristics based on the I2t
characteristics of cables as per IEC 60269-2. In case of a short circuit, the thyristor will blow before the fuse. However,
2
a semiconductor back-up (or a high speed) fuse has a time characteristics based on I t characteristics of a thyristor.
Hence, semiconductor fuse or high speed fuse can protect the thyristor module.

Forced cooling for TSM

Being electronic switches, the heat generated due to losses needs to be dissipated quickly. The thyristor switching
modules are generally designed with fins for better heat dissipation. They should be mounted in a position so that
maximum air flow is possible. Additionally, it is always recommended to use an adequately-sized fan in the
compartment where TSMs are mounted in an APFC panel.

Some thyristor switching modules come with in-built fans for cooling. Practically, it is difficult to spot a fan failure in
such a case and an undetected fan failure may lead to failure of TSM. The TSM module becomes unnecessarily bulky
in such cases. Hence, it is best to use fan-less modules with an adequately-sized fan on panel ceiling.

How to Connect

Capacitor
branch A TSM is connected to the line via a semiconductor fuse
L1 (R)
L2 (S) and its output is given to the three-phase capacitor or a
L3 (T)
N detuned filter (in case harmonics are present).
PE
input X1 (signal)
Triggering of a TSM can be done by means of dynamic
Fuse superfast (controller signal)
100A at 50kVAr power factor controllers. Triggering can be done by a
80A at 25 kVAr + -

32 / 35A at 25 kVAr
Signal
10-24 VDC controller which has a transistor output. Typically, a
TSM has a 24 V or/and a 12 V input and the respective
L1 fault -on L3 fault -on
operation operation

LTTSM
Electronic thyristor-module
for capacitor switching currents required for triggering are approximately 15
mA and 20 mA respectively. Sometimes, more than
one TSM is required to be connected to the same
controller output for making a larger step, say, 100
C1 L1 L3 C3 kVAr. In such a case, more than one TSM can be
connected to one output of the controller. The
maximum number of TSMs that can be connected to a
0.2% series Reactor / controller is restricted by the dc supply available and the
7% Detuned Reactor
maximum current limit of a stage output of the
Quick Discharge Resistor (QDR)
controller output.

Figure 4 Connection Diagram of TSM

67
Another point to be noted here is that in case of TSM, there is no electrical isolation. Due to the switching principle of
the thyristor-modules the PFC-capacitors are permanently loaded at the peak value of the grid voltage (DC current)
even when they are disconnected. Even when the thyristor switches are off, no electrical isolation is given. Hence,
even after switching off the incomer of the APFC system, parts should only be touched after the standard discharge
time of the capacitors.

Combination of Contactor-based & Thyristor-based Panels

Thyristor switching modules being expensive is often a concern for industry. An economical solution without
compromising the performance of power factor correction panel can still be devised in many applications. Typically,
an industry consists of a variety of loads – some fixed loads that are always running, some varying motor loads that
run for some part of the day and some highly fluctuating loads.
The following solution is suggested:

APFC CONTROLLER

Fixed Compensation Contactor-based switching Thyristor-based switching

for fixed load for variable load for fluctuating load

Figure 5: Combination of Contactor-based and Thyristor-based switching

The most economical solution can be to provide some fixed capacitors for the loads that are ON throughout the day,
a contactor-based switching for capacitors providing compensation to varying motor loads and a thyristor-based
switching for capacitors providing compensation to highly fluctuating loads.
 THYRISTOR SWITCHING MODULES 68
In some modern industries, due to special processes with rapidly fluctuating
loads, the demand for reactive power also fluctuates rapidly. Usage of
mechanical switch (contactors) has the following negative impacts:
Average unity power factor cannot be maintained due to delay in capacitor
n

switching
Reduction in the life of capacitors, contactors and other equipments
n

Power quality issues due to current and voltage transients

n

The solution is dynamic power factor correction system.

With the thyristor module we provide the main component - “The Electronic Switch”- for dynamic power factor
correction. The LT-TSM series offers fast electronically controlled, self-observing thyristor switches for capacitive
loads up to 50 kVAr, that are capable to switch PFC capacitors within a few milliseconds nearly without a limitation to
the number of switchings during the capacitor lifetime. These switching modules are easy to install, have a fast
reaction time of 5 msec and come with built-in indications of operations, faults and activation. These thyristor
modules are very compact and operate at lower power losses.

Features
High peak inverse voltage (2.2 kV) ensures long operational life
n

Automatic thermal cut-off

n

Monitoring of voltage, phase sequence, faults and display of status via LED
n
Faster response time - 5 ms
n

No system perturbation caused by switching operations (no transients)

n
No auxiliary supply needed
n
Maintenance free
n
Long operational life
n

High switching speed

n
No noise during switching
n
Compact design ready for connection and easy installation
n

Application
Industries and applications with high load fluctuations, where the demand for reactive power is also very
dynamic:
Welding
n

Elevators and cranes

n

Presses
n
Wind turbines
n
69
Technical Details
LT TSM 10 LT TSM 25 LT TSM 50
Rated Voltage (V) 440 V
Frequency (Hz) 50 / 60
Rating (kVAr) 10 25 50
Power Losses (W) 35 75 150
LED Display Per Phase 2 2 2
Ambient Temperature (0C) -10 to 55
Signal Voltage Required 10-24 Vdc (20 mA)
Peak Inverse Voltage (PIV) 2.2 kV
Reaction Time 5 ms
Re-switching Time 60 ms
2 LEDs Per Phase
LED (Green/Red) Fault / Operation
Green : Operating voltage activated, thyristor module standby
Flashing Red - Fast : Temperature failure
Indication / Display Flashing Red - Slow : Net voltage L1-L3 too low (under-voltage < 300 V)
Permanent Red : Phase L2 missing or under-voltage
or phase L1 or L3 missing or capacitor without capacitance or not existent
LED (Yellow)
Yellow : “Module ON”

Permanent monitoring of net voltage, temperature and operation status

Monitoring
(Note: Before re-switching after temperature fault, heat sink temperature must be below 50°C)

Termination Connection from bottom; Cable lug: 25 sq. mm. D: 8 mm

Semiconductor fuse (High speed fuse) is mandatory for short circuit protection.
Protection
10 kVAr : 32 A 25 kVAr : 80 A 50 kVAr : 160 A
Capacitor Discharge Resistor Quick discharge resistors (Default capacitor discharge resistors shall be interchanged with QDR)
Mounting Position Vertical, minimum 100 mm space clearance around the module

Selection of TSM and Semiconductor Fuse

Capacitor Step (kVAr) Rated Current (A) TSM Rating (kVAr) Semiconductor Fuse Rating (A)
5 6.6 10 16
10 13.1 10 32
12.5 16.4 25 40
15 19.7 25 47
20 26.2 25 63
25 32.8 25 80
30 39.4 50 94
35 45.9 50 110
40 52.5 50 126
50 65.6 50 160
75 98.4 3 nos. of 25 9 nos. of 80 A
100 131.2 2 nos. of 50 6 nos. of 160 A
 70
Network of Thyristor Switching Modules

supply meas.
voltage voltage meas. current
Vb Vm Im (5A/1A) 1st Capacitor 2nd Capacitor 3rd Capacitor
branch branch branch
L1 k

L2 (S)

L3 (T)
N

PE

Semi conductor fuse Semi conductor fuse Semi conductor fuse

T2A

T2A

160 A at 50 kVAr
80 A at 25 kVAr

Input
(controller signal)

+- +- +-
Signal Signal Signal
10-24VDC 10-24VDC 10-24VDC

L N L N K I L1 fault /”On” L3 fault /”On” L1 fault /”On” L3 fault /”On” L1 fault /”On” L3 fault /”On”
operation operation operation operation operation operation

U Um lm
LT TSM LT TSM LT TSM
Alarm electronic thyristor-module
for capacitor switching
electronic thyristor-module
for capacitor switching
electronic thyristor-module
for capacitor switching

a b P1 1 2 3 4 5 6

C1 L1 L3 C3 C1 L1 L3 C3 C1 L1 L3 C3

+-
24 V DC

Filter

Quick Discharge
Resisto (QDR)

Power
Capacitor

Thyristor Switching Modules - Dimensions

H
H

Top View
C1 L1 L3 C3

W D

Front View Side View

Rating Max. RMS Current Dimensions in (mm)

(kVAr) (A) Cat. Nos.
W D H
10 20 153 75 153 LTTSM10B2
25 50 156 171 200 LTTSM25B2
50 100 156 171 200 LTTSM50B2
 etaCON M - AUTOMATIC POWER FACTOR
CORRECTION CONTROLLER 72
The etaCON M Series are micro-processor based power factor controllers
which automatically correct power factor, with the help of contactors by
switching the required number of capacitor banks.

The etaCON M controller offers power factor correction without any need for
manual intervention. It decides the optimum configuration of capacitor banks
to achieve desired power factor by taking into consideration the kVAr of each
step, the number of operations, total usage time, re-connection time of each
step, etc. The intelligent adjustment interface helps in achieving balanced
capacitor usage ensuring longer life for switchgear and capacitors. Besides,
manual switching of capacitors is also possible directly through the controller.
The maximum no. of steps in etaCON M Series can go up to 14.

The etaCON M Series is modular in design. The base controller comes with 3
steps, 5 steps (96 x 96 mm) and 8 steps (144 x 144 mm). The functionality of
these base controllers can be enhanced with help of Plug-in Modules.
“etaCON M - 3 step controller (96 x 96)” can accommodate 1 plug-in module
and thus is expandable up to 6 steps.“etaCON M - 5 step controller (96 x 96)”
can accommodate 1 plug-in module and thus is expandable up to 8 steps.
“etaCON M - 8 step controller (144 x 144 mm)” can accommodate up to 2
plug-in modules and thus is expandable up to 14 steps. The following table
provides description of Plug-in Modules:

Plug-in Module Type Description

2 steps Plug-in Module 2 Relay outputs

3 steps Plug-in Module 3 Relay outputs

RS485 Plug-in Module RS485 Module for communication on Modbus Rs485

Salient Features

BACKLIT LCD DISPLAY

Backlit icon LCD with excellent information display. In
presence of alarm, a scrolling text appears on screen. All
parameters can be viewed on the screen, at a single go

COMPACT RELAY

Compact Relay of 96x96 (WxH in mm) for 3 steps & 5 steps

(extendable upto 8 steps) and 144 x 144 (WxH in mm) for
8 steps (extendable upto 14 steps) for space economy
73

MEASUREMENT OF I-THD AND V-THD

etaCON M relay can measure I-THD and V-THD

MAN
upto 15th order.
MODE AUT

CONTROLLER
AUTOMATIC POWER FACTOR

etaCON M detects the CT reversal and automatically

AUTOMATIC RECOGNITION OF corrects the same. This saves the effort put into the
CURRENT FLOW DIRECTION detection/correction of CT polarity at site.

DISPLAY OF AVERAGE WEEKLY POWER FACTOR

Average value of power factor of last seven days is
MODE
MAN
AUT displayed and updated every day for assessment of
APFC panel performance.
OR CONTROLLER
AUTOMATIC POWER FACT

Hunting of capacitors is avoided by faster switching of

INTELLIGENT SWITCHING step in case of higher kVAr demand and more delay in
SENSITIVITY case of smaller demand.

KEYPAD LOCK
MODE
MAN
AUT The keypad lock function eliminates unauthorized
modification of operating parameters.
CONTROLLER
AUTOMATIC POWER FACTOR
 74

PROVISION OF ALARMS

MODE
MAN
AUT
Alarms for Under/Over compensation, Low/High current,
Low/High voltage, Capacitor overload due to harmonic
AUTOMATIC POWER FA
CTOR CONTROLLER
voltage, over temperature, V-THD too high, I-THD too
high, Maintenance request, Step failure.

etaCON M measures the percentage of the residual

power of the steps which is compared with the original
CAPACITOR HEALTH MONITORING power programmed value. When the percentage results
to be below the threshold set, the step failure alarm gets
activated.

PROTECTION OF PANEL FROM OVER-HEATING

An inbuilt temperature sensor monitors temperature variation of

MAN
MODE AUT
the panel. Alarm is triggered in case of over-heating. Fan start &
stop temperature can be set to operate cooling fans.
CTOR CONTROLLER
AUTOMATIC POWER FA

HT AND LT SENSING

Sensing at LT Sensing at HT

S1
etaCON M
Relay
Main
S2
Voltage
Input
VT1
Main

Transformer Transformer

S1
etaCON M Load
Load Relay
S2
Voltage
Input
75
Technical Specifications
Parameter etaCON M with 3 steps & 5 steps etaCON M with 8 steps

No. of steps* 3, 5, 6, 7, 8 8, 10, 11, 12, 13, 14

Design Digital microprocessor based

Display LCD Display

Size (W x H in mm) 96 x 96 144 x 144

PF, V, I, Required kVAR, capacitor overload, Panel Temperature, Average Weekly PF,
Measurements th
No. of switching of each step, V-THD & I-THD up to 15 order

Maximum voltage and current value, Maximum capacitor overload value,

Metering/Logging
Maximum panel temperature value

Target PF adjustment: 0.5 Inductive to 0.5 Capacitive

Settings Reconnection time of same capacitor - 1 to 30000s

Switching time sensitivity - 1 to 1000s

Under/Over Compensation, Low/High Current, Low/High Voltage, Capacitor Overload,

Alarms
Over temperature, Voltage THD too high, Current THD too high

Supply

Auxiliary Voltage 100 - 440V ~

Frequency 45 - 66Hz

100V: 2W - 4VA
Power consumption/dissipation 3.5W - 9.5VA
440V: 3W - 8.5VA

No-voltage release >= 8ms

Immunity time for microbreakings <= 25ms
Voltage inputs

Maximum rated voltage Ue 600VAC L-L (346VAC L-N)

Measuring range 50-720V L-L (415VAC L-N)

Frequency range 45-65Hz

Measuring method True RMS

> 0.55MΩ L-N

Measuring input impedance > 15MΩ
> 1.10MΩ L-L
Accuracy of measurement 1% ±0.5 digit
Current inputs

Rated current Ie 1A ~ or 5A ~

For 5A scale: 0.025 - 6A ~

Measuring range
For 1A scale: 0.025 – 1.2A ~
Type of input Shunt supplied by an external current transformer (low voltage). Max 5A
Measuring method True RMS
Overload capacity +20% Ie
Overload peak 50A for 1 second
Accuracy of measurement ± 1% (0.1-1.2In) ±0.5 digit
Power consumption <0.6VA

Relay output: Output 1-2 of M3 / output 1-4 of M5 Output 1-7

Contact type 4 x 1 NO + contact common 7 x 1 NO + contact common

"B300, 5A 250V~
UL Rating B300, 30V= , 1A Pilot Duty
30V= 1A Pilot Duty, 1.5A 440V~ Pilot Duty"

Max rated voltage 440V~

Rated current AC1-5A 250V~ AC15-1.5A 440V~
Maximum current at contact common 10A
Mechanical / electrical endurance 1x10 / 1x105 ops
7
 76

Relay output: Output 3 of M3 / Output 5 of M5 Output 8

Contact type 1 changeover 1 changeover

B300, 5A 250V~
UL Rating B300 / 30V=1A pilot duty
30V=1A Pilot Duty, 1.5A 440V~Pilot Duty

Max rated voltage 415V~ 440V~

Rated current AC1-5A 250V~AC15-1.5A 440V~

7 5
Mechanical / electrical endurance 1x10 / 1x10 ops

Insulation

Rated insulation voltage Ui 600V

Rated impulse withstand voltage Uimp 9.5kV
Power frequency withstand voltage 5.2kV
Ambient conditions

Operating temperature -20°C to +60°C

Storage temperature -30°C to +80°C
Relative humidity <80% (IEC/EN 60068-2-78)
Maximum pollution degree 2
Overvoltage category 3
Measurement category III
Climatic sequence Z/ABDM (IEC/EN 60068-2-61)
Shock resistance 15g (IEC/EN 60068-2-27)
Vibration resistance 0.7g (IEC/EN 60068-2-6)
Connections

Terminal type Plug-in / removable

Conductor cross section (min-max) 0.2-2.5 mm2(24-12 AWG)
Tightening torque 0.56 Nm (5 lbin / 4-5 lbin per UL) 0.56 Nm (5 lbin)

Housing

Version Flush mount

Material Polycarbonate

IP54 on front with gasket, if mounted in IP65 on front with gasket if installed in a panel
Degree of protection
class IP54 panel or better - IP20 terminals with the same IP protection - IP20 terminals

Weight 320g 640g

Certifications and compliance

Comply with standards IEC/EN 61010-1, IEC/EN 61010-2-30, IEC/EN 61000-6-2, IEC/EN 61000-6-4
* Refer Selection Guideline at Page 78
77
Wiring Diagrams

etaCON M – 3 Steps & 5 Steps

MAINS
1 2 3
N L1 L2 L3
1 2 3 4 5
INPUT INPUT AUX
CURRENT VOLTAGE~ SUPPLY
S1 S2 100-600V 100-440V~

14 13 3 4 1 2 5 6 7 8 9 10 11 12

F6 F7
2x2A 2x2A

CT1

MCCB

MO C1 F1 MO C2 F2 MO C5 F5
R R R

K1 K2 K5

LOAD

kVAr1 kVAr2 kVAr5

etaCON M - 8 steps

MAINS
N L1 L2 L3 1 2 3 4 5 6 7 8
INPUT INPUT AUX
CURRENT VOLTAGE~ SUPPLY
S1 S2 100-600V 100-440V~

1 2 4 5 6 7 15 8 9 10 11 12 13 14 16 17 18

F9 F10
2x2A 2x2A

CT1

MCCB

MO C1 F1 MO C2 F2 MO C8 F8
R R R

K1 K2 K8

LOAD

kVAr1 kVAr2 kVAr8

Note: 1. The polarity of current/voltage input is irrelevant.

2. CT can be connected to any one of the three phases. The voltage input must be connected to the other two remaining phases.
 78
Overall Dimensions
etaCON M - 3 Steps & 5 steps 92
65
96 8.5
55

92
96

Plug-in Module

etaCON M - 8 steps
43.3 138
144 10
137

138
144

Module
Plug in
64.5

35
73 Dimensions in mm

etaCON M Series - APFC Relay Selection Guideline

Steps Size Cat. No.
Steps Combination
Description (W x H in mm) Combination

3 2+1* 96 x 96 3 Step APFC Relay ETACONM003R

5 4+1* 96 x 96 5 Step APFC Relay ETACONM005R

6 5+1* 96 x 96 3 Step APFC Relay + 3 Step Plug-in module ETACONM003R + ETACONEXP3R

7 6+1* 96 x 96 5 Step APFC Relay + 2 Step Plug-in module ETACONM005R + ETACONEXP2R

8 7+1* 96 x 96 5 Step APFC Relay + 3 Step Plug-in module ETACONM005R + ETACONEXP3R

8 7+1* 144 x 144 8 Step APFC Relay ETACONM008R

10 9+1* 144 x 144 8 Step Controller+2 Step Plug-in module ETACONM008R + ETACONEXP2R

11 10+1* 144 x 144 8 Step Controller+3 Step Plug-in module ETACONM008R + ETACONEXP3R

12 11+1* 144 x 144 8 Step APFC Relay + 2 Step Plug-in module + 2 Step Plug-in module ETACONM008R + ETACONEXP2R + ETACONEXP2R

13 12+1* 144 x 144 8 Step APFC Relay + 2 Step Plug-in module + 3 Step Plug-in module ETACONM008R + ETACONEXP2R + ETACONEXP3R

14 13+1* 144 x 144 8 Step APFC Relay + 3 Step Plug-in module + 3 Step Plug-in module ETACONM008R + ETACONEXP3R + ETACONEXP3R

*Last Contact can be programmed for capacitor switching / Alarm function / Fan control

Ordering information:
etaCON M APFC Relay etaCON M Optional Plug-in Modules
CT Voltage Description
Model Secondary Input Cat. No. Model Cat. No.
3 Step APFC Relay
(96 x 96) ETACONM003R 2 Step Plug-in Module 2 Relays NO ETACONEXP2R
5 Step APFC Relay
(96 x 96) 1A/5A 415V / 110V ETACONM005R 3 Step Plug-in Module 3 Relays NO ETACONEXP3R
8 Step APFC Relay ETACONRS485
(144 x 144) ETACONM008R RS485 Plug-in Module RS485 Plug-in Module
 SELECTION OF CAPACITOR - 5 STEP APPROACH 80
Power Factor Correction Capacitors have been used for many years as the most cost effective solution for PF
improvement. Modern electrical networks are continuously evolving into more complex installations due to the
increasing usage of non-linear loads, sophisticated control & automation, UPS systems, energy efficiency
improvement devices etc.
This evolution is also accompanied by increased dependency on captive power generation as well as growing
concerns about incoming supply power quality.
In this background, it is necessary to evolve the Power Factor Correction solution also to a higher level so as to ensure
sustainable achievement of high PF & acceptable harmonic distortion levels.
The selection of the correct type of PFC capacitors & filter reactors thus needs better understanding of the various
issues involved.
This publication outlines a “5 Step” technology based approach, simplified for easier understanding to enable the
correct selection of PFC Capacitors & Filter Reactors.

STEP 1 STEP 2
Calculation Selection of
of kVAr Required Capacitor Duty

SELECTION
OF CAPACITORS

STEP 5 STEP 3
Achieving Dynamic Avoiding the Risk of
and Transient Harmonic Application
Free Unity PF and Resonance
STEP 4
Methods of Power
Factor
Correction

STEP 1: Calculation of kVAr Required for Industries & Distribution Networks

In electrical installations, the operating load kW and its average power factor (PF) can be ascertained from the
electricity bill. Alternatively, it can also be easily evaluated by the formula:
Average PF = kW/kVA
Operating load kW = kVA Demand x Average PF
The average PF is considered as the initial PF and the final PF can be suitably assumed as target PF. In such cases,
required capacitor kVAr can be calculated as explained in the example below:
Example: To calculate the required kVAr compensation for a 500 kW installation to improve the PF from
0.75 to 0.96
kVAr = kW x multiplying factor from table = 500 x 0.590 = 295 kVAr
Note: Table is based on the following formula:

where
kVAr required = kW (tanØ1 - tanØ2) Ø1 = cos-1 (PF1) and Ø2= cos-1(PF2).
81
Target
PF 0.9 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99
Initial
PF
0.4 1.807 1.836 1.865 1.896 1.928 1.963 2.000 2.041 2.088 2.149

0.42 1.676 1.705 1.735 1.766 1.798 1.832 1.869 1.910 1.958 2.018

0.44 1.557 1.585 1.615 1.646 1.678 1.712 1.749 1.790 1.838 1.898

0.46 1.446 1.475 1.504 1.535 1.567 1.602 1.639 1.680 1.727 1.788

0.48 1.343 1.372 1.402 1.432 1.465 1.499 1.536 1.577 1.625 1.685

0.5 1.248 1.276 1.306 1.337 1.369 1.403 1.440 1.481 1.529 1.590

0.52 1.158 1.187 1.217 1.247 1.280 1.314 1.351 1.392 1.440 1.500

0.54 1.074 1.103 1.133 1.163 1.196 1.230 1.267 1.308 1.356 1.416

0.56 0.995 1.024 1.053 1.084 1.116 1.151 1.188 1.229 1.276 1.337

0.58 0.920 0.949 0.979 1.009 1.042 1.076 1.113 1.154 1.201 1.262

0.6 0.849 0.878 0.907 0.938 0.970 1.005 1.042 1.083 1.130 1.191

0.62 0.781 0.810 0.839 0.870 0.903 0.937 0.974 1.015 1.062 1.123

0.64 0.716 0.745 0.775 0.805 0.838 0.872 0.909 0.950 0.998 1.058

0.66 0.654 0.683 0.712 0.743 0.775 0.810 0.847 0.888 0.935 0.996

0.68 0.594 0.623 0.652 0.683 0.715 0.750 0.787 0.828 0.875 0.936

0.7 0.536 0.565 0.594 0.625 0.657 0.692 0.729 0.770 0.817 0.878

0.72 0.480 0.508 0.538 0.569 0.061 0.635 0.672 0.713 0.761 0.821

0.74 0.425 0.453 0.483 0.514 0.546 0.580 0.617 0.658 0.706 0.766

0.75 0.38 0.426 0.456 0.487 0.519 0.553 0.590 0.631 0.679 0.739

0.76 0.371 0.400 0.429 0.460 0.492 0.526 0.563 0.605 0.652 0.713

0.78 0.318 0.347 0.376 0.407 0.439 0.474 0.511 0.552 0.699 0.660

0.8 0.266 0.294 0.324 0.355 0.387 0.421 0.458 0.499 0.547 0.608

0.82 0.214 0.242 0.272 0.303 0.335 0.369 0.406 0.447 0.495 0.556

0.84 0.162 0.190 0.220 0.251 0.283 0.317 0.354 0.395 0.443 0.503

0.85 0.135 0.164 0.194 0.225 0.257 0.291 0.328 0.369 0.417 0.477

0.86 0.109 0.138 0.167 0.198 0.230 0.265 0.302 0.343 0.390 0.451

0.87 0.082 0.111 0.141 0.172 0.204 0.238 0.275 0.316 0.364 0.424

0.88 0.055 0.084 0.114 0.145 0.177 0.211 0.248 0.289 0.337 0.397

0.89 0.028 0.057 0.086 0.117 0.149 0.184 0.221 0.262 0.309 0.370

0.9 0.029 0.058 0.089 0.121 0.156 0.193 0.234 0.281 0.342

0.91 0.030 0.060 0.093 0.127 0.164 0.205 0.253 0.313

0.92 0.031 0.063 0.097 0.134 0.175 0.223 0.284

0.93 0.032 0.067 0.104 0.145 0.192 0.253

0.94 0.034 0.071 0.112 0.160 0.220

0.95 0.037 0.078 0.126 0.186

 82
Step 2: Selection of Capacitor Duty
The criteria for this classification is based on the following:
n Operating life
n Permissible over voltage & over current coupled with the time duration
n Number of switching operations per year
n Peak inrush current withstand capability
n Operating ambient temperature

Comparison of technical parameters

Permissible Over Peak Maximum
Over Ambient
Duty Voltage @ Rated Inrush Switching Life
Current Temperature
Voltage 440V Currents Operations / Year

Standard Duty 1.5 x In 1.1 Un (8h/24h) 200 x In -25°C to 55°C 5000 1,00,000 hrs

Heavy Duty 1.8 x In 1.1 Un (8h/24h) 300 x In -25°C to 55°C 8000 1,50,000 hrs

2,25,000 hrs at 400-60°C;

Super Heavy duty 2.5 x In 1.1 Un (8h/24h) 350 x In -40°C to 65°C 15000
1,50,000 hrs at 40/-65°C

LTXL: Ultra Heavy Duty 3 x In 1.1 Un (8h/24h) 500 x In -25°C to 65°C 20000 3,00,000 hrs

Step 3: Avoiding the Risk of Harmonic Amplification and Resonance

This step is to make a choice between the use of Capacitors or Capacitors + Filter reactors.
In a system with inductive (XL) and capacitive (XC) impedances, resonance can happen at one particular frequency
(resonant frequency, fR).
Ohms

XC XL

1
Resonant frequency, fR= Z XL-XC
(2 LC )
R

ƒ (Hz)
ƒr

At this point XL becomes equal to XC and the net impedance becomes very low. Hence, at resonance point, the
magnitude of the current (with frequency fR) is very high and only inherent resistance in the network would limit the
current. Typically, the resonance may create major problem in harmonics rich industry. The resonant frequency may
match with any of the harmonic frequency and create very high harmonic amplification, which can create huge
damage to the electrical equipment.

Addition of detuned reactors (in series to capacitors) forcefully shifts the resonant frequency to a safer level.
For example, combination of capacitor and 7% detuned filter reactor has the resonant frequency of 189 Hz, which
will avoid resonance with 5th harmonic and above.

Solutions for Current & Voltage Harmonics

Current Harmonics Voltage Harmonics
(VTHD) Recommended Solutions**
(ITHD)

Detuned Harmonic Filter with 480 V (SHD/LTXL) Capacitors and/or

High Low (£
5%)
Active Harmonic Filter

High High (>5%) Active Harmonic Filter and 525 V (SHD/LTXL Cyl) Capacitors

Grid may be polluted with imported voltage harmonics. It may not be

Low High (>5%)
possible to reduce them at the load side. Check with utility to rectify

**These are typical solutions. However the actual solution may vary depending up on the actual harmonic content in the system.
83
Step 4: Methods of Power Factor Correction
This aims at estimating whether fixed compensation or automatic compensation is to be used.
In order to achieve high power factor i.e., close to unity PF, the following guideline may be adopted to make a
decision. If the total kVAr required by the installation is less than 15% of the rating of the incoming supply
transformers, then the use of fixed capacitors may be adopted at various points in the installation.
If the kVAr required by the installation is more than 15% of the rating of the incoming supply transformers, then
automatic power factor correction solution needs to be adopted.
APFC panels with suitable kVAr outputs may be distributed and connected across various points within the
installation.
Note: De-tuned filter APFC panels must be selected if non-linear loads are present in the system.

Methods of Power Factor Compensation

Individual Group Central
Compensation Compensation Compensation

Manual / Manual /
Control Automatic
Semi-automatic Semi-automatic
Elimination of Supply Bus
Yes Yes Yes
penalties due to low PF
Achievement of
No No Yes
Unity PF
Transformer
Optimization of the kVA
demand of the installation Yes Yes Yes
to the installed load in kW
Circuit breaker
Reduction of transformer
Yes Yes Yes
loading
Reduction of transformer
Yes Yes Yes
losses CC

Reduction of circuit
Yes Yes Yes
breaker rating
Reduction of switchgear GC GC
ratings and cable sizes Yes Partial reduction No
down the line
IC IC IC IC
Reduction in I2R losses Yes Partial reduction No
Chance of leading PF No Yes No
L L L L

Simple and Relatively Best suited for

Advantages inexpensive better industries
for few number management with large and L : Inductive load
of motors of loads variable loads
IC : Individual Compensation
Difficult to GC : Group Compensation
Managing manage,
becomes difficult Relatively CC : Central Compensation
Disadvantages if there is load
if the number of expensive
variation
motors are more in the group

Step 5: To Achieve Dynamic and Transient Free Unity PF

Conventional switching techniques of capacitors involving electro-mechanical contactors may give rise to transient
phenomena. This transient phenomena can interact with impedances present in the installation to create “Surges”.
This occurrence of surges can cause serious damage to sensitive electronics and automation resulting in either their
malfunction or permanent damage. The transient phenomenon is a sudden rise in voltage or current at the point of
switching.
In this background, it is important to ensure that all the capacitors installed are switched in a transient free manner so
as to ensure reliable performance of the installation.
In such a situation, it is necessary to specify the use of Thyristor switches for transient free switching of Capacitors.
Note: Thyristor switching can also be used for dynamic compensation which is needed if the fluctuation of loads is
very high; such as lifts, welding load is very high; fast presses etc.
 MOTOR POWER FACTOR COMPENSATION 84
The various methods of power factor correction are direct compensation, group compensation and centralized
compensation. Depending upon the size and the rate of change of loads in an industry, any one or combination of
the above methods can be employed. Specifically, in case of agricultural pump-sets and some small scale industries
with a few motor loads, the power factor correction can be done by connecting shunt capacitors directly to the
motors. This method of compensation is called direct compensation. This is simple and ideal method for reactive
power compensation, as this results in rating optimization of all the upstream switchgear and cables, which reduces
overall system losses.

Direct motor compensation can be done by two methods:

Method – 1:
As shown in the figure, the capacitor is connected directly to the motor terminals, after the starter. The capacitors
would start supplying reactive power, as soon as the motor is switched ON. This method of compensation can be
used for motors with Direct on-line starters. Usually the kVAr rating for a particular motor is given by the respective
motor manufacturers, as the kVAr ratings are motor specific.

Motor 3000 1500 1000 750 500

(hp) rpm rpm rpm rpm rpm
2.5 1 1 1.5 2 2.5
5 2 2 2.5 3.5 4
7.5 2.5 3 3.5 4.5 5.5
10 3 4 4.5 5.5 6.5
15 4 5 6 7.5 9
20 5 6 7 9 12
25 6 7 9 10.5 14.5
30 7 8 10 12 17
40 9 10 13 15 21
50 11 12.5 16 18 25
60 13 14.5 18 20 28
70 15 16.5 20 22 31
Starter 80 17 19 22 24 34
90 19 21 24 26 37
100 21 23 26 28 40
110 23 25 28 30 43
120 25 27 30 32 46
130 27 29 32 34 49
140 29 31 34 36 52
145 30 32 35 37 54
150 31 33 36 38 55
M 155 32 34 37 39 56
160 33 35 38 40 57
165 34 36 39 41 59
170 35 37 40 42 60
175 36 38 41 43 61
c
180 37 39 42 44 62
185 38 40 43 45 63
190 38 40 43 45 65
200 40 42 45 47 67
250 45 50 55 60 70

Even though this is the effective method of power factor compensation, there is a limitation in sizing of the
capacitors. That is, the maximum kVAr should be decided such that, the rated capacitor current is less than 90% of
the motor’s no-load current. If this condition is not met, self-excitation may occur, in which the motor acts as a
generator. This happens when a motor has enough inertia to keep rotating even after being disconnected from the
power system and the capacitor is large enough to supply the reactive power needs of the motor. Self-excitation may
result in high voltage at the terminals of the motor and this can damage the contactor and the capacitor. As this
method has the limitation in the sizing of maximum kVAr rating, it is not possible to achieve unity power factor.
85
Method – 2:
In this method, the capacitor is connected to the motor before the starter and it is switched through a separate
capacitor-duty contactor. The capacitors are disconnected as soon as the motor is switched off hence, self-excitation
is avoided. There is no need of any limitations in capacitor sizing and unity power factor can be achieved by this
method.
The capacitor size (in kVAr) can be calculated by the below formula:
kVAr = kW (tan f
1 -
tanf
2)
-1 -1
where, F
1 = cos (Initial PE) and F
2 = cos (Target PF)

The limitations are the manual switching of the capacitors and the extra cost incurred for the contactors. Moreover,
when the number of motors increase in future, managing all at a time would be difficult.

Motors with Star-Delta Starter

Specifically for motor with star-delta starter, it is recommended to use method-2. If capacitors are directly connected
to the terminals of the motor, the life of the capacitor drops drastically because of the voltage spikes that happen
during every star to delta transition. So it is safer to connect the capacitor before the star-delta starter, as shown in the
above figure.

Points to remember
• The operating power factor varies with respect to the percentage loading of the motors. Hence with the varying
load, the fixed capacitors may not be able to maintain the unity power factor continuously.
• After switching off the capacitor, it is very important to maintain a minimum time delay of 60 seconds, for
switching ON the capacitor again. Else, there are more chances of contactor damage because of charged
capacitor.
• If the motor is operated with drives/converters, it is recommended to detune the capacitors by adding series
reactors.
• It is recommended to use capacitor duty contactors for minimizing the inrush current and hence to maximize the
life of contactors and the capacitors.
 TRANSFORMER COMPENSATION 86
In order to achieve near unity power factor, all sources of reactive power need to be identified and fully
compensated. One such element that consumes reactive power is the transformer. Reactive power is consumed by
transformers through the no load magnetizing current and through the leakage reactance. This article is aimed at
helping customers size capacitor banks for transformer compensation.

Basics
The power factor on the HT side (source side) of a transformer depends upon the following:
• LT Side (Load side) power factor
• Real power consumed by transformer
• Reactive power consumed by transformer
The load side power factor is compensated by employing APFC panels and/or by providing individual compensation
to connected loads. Transformer compensation on the other hand needs a different approach.
The equivalent circuit of a transformer is as shown below:
Lleakage RT
IL
VP IO
VS
Source Load
side RNL Lmag side

IW IM

Where: VP is the source voltage, VS is the load voltage, IO is the no load current, IW is the no load watt loss
current, IM is the magnetizing current, RNL is the no load resistance, Lmag is the magnetizing inductance, Lleakage is the
leakage inductance, RT is the windingresistance.
As can be seen from the equivalent circuit, the inductive elements, namely Lmag and Lleakage contribute to the VAR
consumption of the transformer

Magnetizing VAR Requirement of A Transformer

The magnetizing VAR consumption is a function of the rated voltage and the magnetizing current of the
transformer. The no load current of a transformer varies between 0.5 % and 2.5% of the full load current depending
on the design of the transformer and the operating flux level. The magnetizing current is around 80% of the no load
current and thus varies between 0.4% and 2%. It is safe to assume a value of 1-1.2% for distribution transformers.
Thus the VAR required to compensate for the magnetizing current of the transformer is around 1- 1.2% of the
transformer kVA rating.

VAR Requirement Due to Leakage Reactance

The VAR requirement due to leakage reactance is a function of the square of the current and the leakage reactance.
At full load the voltage drop across the leakage reactance is equal to the impedance voltage (%Z impedance). The
reactive VAR consumption is equal to the product of impedance voltage and load current.
2
Qx =LL x x Leakage;
Where IL is the load current and XLeakage is the leakage reactance; QX is the kVAr

Power Requirement
Typically, for a 3 phase transformer,
2
V2
Xleakage = x (%Z);
kVA
Where V2 is the secondary voltage.
Qx = (%Z) x (kVA) x (%load)2
% loading is assumed to be 50% to 75%. Thus for % Z=5%, Q works out to 5%* (75%) i.e. 3%
Thus the VAR requirement to compensate for the leakage reactance of the transformer is around 3% of the kVA
rating of the transformer.
The total VAR required to compensate for the reactive power consumed by the transformer is around 4% to 4.25%
of the kVA rating of the transformer.
87 REACTIVE POWER COMPENSATION OF DG SETS
Whenever an industry is drawing power from utility, there are no major complications in managing the reactive
power and power factor close to unity can be maintained. However, when diesel generators are operating, some
precautions are needed to be taken for managing reactive power. This article briefs the performance of the DG sets
at various power factors and thereby shows the optimal manner of power factor compensation of generators with
the help of some examples.
Normally DG sets are rated in apparent power (kVA) along with power factor and typical rated power factor is 0.8 lag
(considering the power factor of motors, without any capacitors) irrespective of alternator’s apparent power. The
diesel engine’s mechanical output power (bhp/kW) is designed to match the electrical real power (kW = kVA x PF) of
the alternator.
For example, consider a generator rated for 1000 kVA and lagging power factor of 0.8. The maximum possible real
power (kW) the generator can supply is 800 kW (rated current = 1739 A). Thus, the diesel engine will also be rated to
deliver 800 kW equivalent mechanical power to the alternator. The following cases show the operation of the
alternator at different power factor.

Case 1:
Apparent power = 1000 kVA; connected load = 800 kW; power factor = 0.8
Current drawn, I1 = 1000 x 1000 / (1.732 x 415 x 0.8) =1739 A
• Here, the generator is operated at the rated name plate values. The load draws maximum rated current from the
generator and the generator draws the maximum permissible mechanical power (800 kW) from the diesel engine.

Case 2:
Apparent power = 1000 kVA; connected load = 800 kW; power factor = 0.6
Current drawn, I2 = 1000 x 1000 / (1.732 x 415 x 0.6) = 2318.9 A
• In case 2, the connected load is 800 kW (operated at 0.6 PF) which is equal to the maximum mechanical power
that the engine can deliver. But the actual current drawn by the load is greater than the rated alternator current.
This results in generator overloading. In order to avoid generator overloading, the maximum load (at the same PF)
that can be connected to the generator is 600 kW at 0.6 PF.

• Conversely, if the connected load is 600 kW and if the power factor is at 0.6, the entire generator capacity
(1000 kVA) is blocked for this partial load. If the power factor was to be improved to 0.8, then as in case 1
additional 200 kW load could have been connected to the same generator, thereby increasing the capacity and
productivity of the industry. Moreover, if 600 kW load is operated at unity power factor, the load current (1391 A)
will be reduced by 40%, thereby significant reduction in the copper loss/cable loss. This will result in fuel savings of
the engine. This is what is described in case 3 below.

Case 3:
Apparent power = 1000 kVA; connected load = 800 kW; power factor = 1.0
Current drawn, I3 = 1000 x 1000 / (1.732 x 415 x 1.0) =1391 A
• The genset is connected to its full capacity of 800 kW operating at unity power factor. Unlike case 1, the load
draws 20% less current at UPF (1391 A). This in turn results in significant reduction in copper loss/cable loss and
thereby saving some fuel.
• Here, at UPF, even though the generator can support a load of 1000 kW, the diesel engine is rated to deliver
a maximum mechanical power of 800 kW.
• Even though the current drawn is less than the rated current (1739 A), the genset is delivering its maximum
real power (800 kW).
• Hence at UPF, utmost care should be taken such that the total connected electrical load must not exceed 800 kW.
Otherwise the diesel engine will be overloaded.

Summary
• Close to unity power factor shall be maintained for the loads connected to the DG sets by using capacitors. This
will result in the reduction of copper loss and hence savings in fuel.
• The load (active power) connected to the generator must not exceed the engine’s equivalent kW rating.
 etaSYS-
89 STANDARD AUTOMATIC POWER FACTOR CORRECTION PANELS
Modern power networks cater to a wide variety of electrical and power electronics loads, which create a varying
power demand on the supply system. In case of such varying loads, the power factor also varies as a function of the
load requirements.
It therefore becomes practically difficult to maintain consistent power factor by the use of fixed compensation i.e.
fixed capacitors which shall need to be manually switched to suit the variations of the load. This will lead to situations
where the installation can have a low power factor leading to higher demand charges and levy of power factor
penalties.
In addition to not being able to achieve the desired power factor it is also possible that the use of fixed compensation
can also result in leading power factor under certain load conditions. This is also unhealthy for the installation as it can
result in over voltages, saturation of transformers, mal-operation of diesel generating sets, penalties by electricity
supply authorities etc.
Consequently the use of fixed compensation has limitations in this context. It is therefore necessary to automatically
vary, without manual intervention, the compensation to suit the load requirements. This is achieved by using on
Automatic Power Factor Correction (APFC) system which can ensure consistently high power factor without any
manual intervention. In addition, the occurrence of leading power factor will be prevented.

APFC Panels are Fully Automatic in Operation and can be used to Achieve:
Consistently high power factor under fluctuating load conditions
n

Elimination of low power factor penalty levied by electrical supply authorities

n

Reduced kVA demand charges

n

n Lower energy consumption in the installation by reducing losses

n Preventive leading power factor in an installation

Basic Operation
To continuously sense and monitor the load condition by the use of external CT (whose output is fed to the
n

control relay)
To automatically switch ON and OFF relevant capacitor steps on to ensure consistent power factor
n

To ensure easy user interface for enabling reliable system operations

n

n To protect against any electrical faults in a manner that will ensure safe isolation of the power factor
correction equipment

Salient Features and Advantages

n Pre-selected optimal number of steps and step sizes, for better step resolution and hunt free capacitors
switching
n Ideal switchgear selection for reliable short circuit protection, without nuisance tripping
n Right capacitor-reactor combination selection to prevent harmonic amplification and resonance
n Option of capacitor duty contactor or thyristor switch for transient free switching
n Panels with better electrical, mechanical and thermal design for longer life of capacitors and other components
n Panels are with advanced microcontroller based APFC relay that offers reliable switching operation with four
quadrant sensing
 90
etaSYS Standard APFC Panel Range
kVAr Branch Harmonic
Product Description Capacitors Main Incomer Switching
ratings Protection Filter

Contactor switched 35 to 500 Heavy Duty Gas MCCB - upto 350 kVAr; MO C Capacitor
etaSYS - MH1 MCCB -
standard APFC Panels kVAr filled Capacitors ACB - 400 to 500 kVAr duty contactor

Contactor switched Heavy Duty Gas MO C Capacitor 7% copper

100 to 500 MCCB - upto 350 kVAr;
etaSYS - MH2 standard APFC Panels MCCB
kVAr filled Capacitors ACB - 400 to 500 kVAr duty contactor reactor
with harmonic filters
Contactor switched 35 to 500 Heavy Duty Gas MCCB - upto 350 kVAr; MO C Capacitor
etaSYS - FH1 HRC Fuse -
standard APFC Panels kVAr filled Capacitors ACB - 400 to 500 kVAr duty contactor
Contactor switched Heavy Duty Gas MO C Capacitor 7% copper
100 to 500 MCCB - upto 350 kVAr;
etaSYS - FH2 standard APFC Panels HRC Fuse
kVAr filled Capacitors ACB - 400 to 500 kVAr duty contactor reactor
with harmonic filters
Thyristor switched Heavy Duty Gas Thyristor
etaSYS - 100 to 500 MCCB - upto 350 kVAr; Semiconductor 7% copper
standard APFC Panels filled Capacitors switching
FH3 (RTPFC) kVAr ACB - 400 to 500 kVAr Fuse reactor
with harmonic filters modules
Contactor switched 100 to 500 LTXL - Ultra Heavy MCCB - upto 350 kVAr; MO C Capacitor -
etaSYS - MU1 MCCB
standard APFC Panels kVAr Duty capacitor ACB - 400 to 500 kVAr duty contactor
Contactor switched MO C Capacitor 7% copper
100 to 500 LTXL - Ultra Heavy MCCB - upto 350 kVAr;
etaSYS - MU2 standard APFC Panels MCCB
kVAr Duty capacitor ACB - 400 to 500 kVAr duty contactor reactor
with harmonic filters
Contactor switched 35 to 500 LTXL - Ultra Heavy MCCB - upto 350 kVAr; MO C Capacitor -
etaSYS - FU1 HRC Fuse
standard APFC Panels kVAr Duty capacitor ACB - 400 to 500 kVAr duty contactor
Contactor switched MO C Capacitor 7% copper
100 to 500 LTXL - Ultra Heavy MCCB - upto 350 kVAr;
etaSYS - FU2 standard APFC Panels HRC Fuse
kVAr Duty capacitor ACB - 400 to 500 kVAr duty contactor reactor
with harmonic filters
Thyristor switched Thyristor
etaSYS - 100 to 500 LTXL - Ultra Heavy MCCB - upto 350 kVAr; Semiconductor 7% copper
standard APFC Panels Duty capacitor switching
FU3 (RTPFC) kVAr ACB - 400 to 500 kVAr Fuse reactor
with harmonic filters modules

etaSYS Basic Design Specifications

Power Range 35 kVAr to 500 kVAr (other ratings with customizations available on request)
Rated System Voltage 440 V / 415 V / 400 V / 380 V
Rated Frequency 50 Hz
Incomer Short Circuit Rating > 36 kA
Altitude 1000 m
Duty Continuous
O O
Ambient Temperature -5 C to 45 C
Power Supply Three phase, four line
Relay Current Input Signal – / 5A, from CT on line
The load bearing structure is made of 2 mm sheet steel
The front door and partition are made of 1.6 mm sheet steel
Enclosures
The internal components are accessible on opening the front door
Ingress protection - IP42
Indoor, wall mounted (upto 100 kVAr), floor mounted (100 kVAr and above)
Installation
in a well-ventilated, non-dusty environment, cable entry from bottom

Incomer 3 Pole MCCBs upto 630 A, 3 Pole ACBs above 630 A

1. Heavy duty cylindrical gas filled capacitors
Capacitors
2. LTXL Ultra Heavy Duty Capacitors (see below table for step ratings)
1. Without Reactors
Reactors
2. With 7% Detuned Reactors
1. 3 Pole MO C Capacitor duty contactors of adequate ratings for respective steps
Switching
2. Thyristor Switching Modules of suitable ratings
1. MCCBs for providing short circuit protection and isolation
Branch Protection 2. HRC Fuses of adequate ratings
3. High speed fuse / semiconductor fuse for thyristor switched APFC panels
91
APFC Panel - Overall Dimensions

R Y B

APFCR
H

Air filter
unit

36
20
TH

W D
Front view Side view

Cut out at bottom

Gland plate

Top view

Notes:
nWall mounted : upto 100 kVAr
nFloor mounted : above 100 kVAr
nRecommended front access : 1000 mm
nRecommended side clearance : 1000 mm
nPaint shade : RAL 7032 Powder coated
nTolerance on dimensions : ±10 mm
nCable entry : bottom
 92
etaSYS - MH1 Standard APFC with a combination of Heavy Duty Capacitors & MCCB
Panel
Type of Main Dimension (mm)
Cat. Nos. Rating Step size (kVAr) Steps Switching Reactor
Branch
Device Capacitor Protection Incomer (H x W x D)*
(kVAr)
LTAPMH0351B2 35 2 x 12.5 + 2 x 5 4 Contactor MPPH - DU MCCB dsine MCCB 1100 x 600 x 400
LTAPMH0501B2 50 2 x 12.5 + 2 x 10 + 1 x 5 5 Contactor MPPH - DU MCCB dsine MCCB 1100 x 600 x 400
LTAPMH0751B2 75 2 x 25 + 2 x 10 + 1 x 5 5 Contactor MPPH - DU MCCB dsine MCCB 1200 x 800 x 400
LTAPMH1001B2 100 50 + 25 + 15 + 5 + 5 5 Contactor MPPH - DU MCCB dsine MCCB 1500 x 1000 x 600
LTAPMH1251B2 125 2 x 12.5 + 2 x 25 + 50 5 Contactor MPPH - DU MCCB dsine MCCB 1500 x 1000 x 600
LTAPMH1501B2 150 2 x 12.5 + 3 x 25 + 50 6 Contactor MPPH - DU MCCB dsine MCCB 1800 x 1000 x 600
LTAPMH1751B2 175 2 x 12.5 + 2 x 25 + 2 x 50 6 Contactor MPPH - DU MCCB dsine MCCB 1800 x 1000 x 600
LTAPMH2001B2 200 2 x 12.5 + 25 + 3 x 50 6 Contactor MPPH - DU MCCB dsine MCCB 1800 x 1000 x 600
LTAPMH2251B2 225 2 x 12.5 + 4 x 50 6 Contactor MPPH - DU MCCB dsine MCCB 1800 x 1000 x 600
LTAPMH2501B2 250 2 x 25 + 4 x 50 6 Contactor MPPH - DU MCCB dsine MCCB 1800 x 1000 x 600
LTAPMH2751B2 275 1 x 100 + 3 x 50 + 2 x 12.5 6 Contactor MPPH - DU MCCB dsine MCCB 2100 x 1200 x 600
LTAPMH3001B2 300 1 x 100 + 3 x 50 + 2 x 25 6 Contactor MPPH - DU MCCB dsine MCCB 2100 x 1200 x 600
LTAPMH3501B2 350 1 x 100 + 3 x 50 + 4 x 25 8 Contactor MPPH - DU MCCB dsine MCCB 2100 x 1200 x 600
LTAPMH4001B2 400 2 x 100 + 2 x 50 + 4 x 25 8 Contactor MPPH - DU MCCB ACB 2000 x 1600 x 800
LTAPMH4501B2 450 2 x 100 + 4 x 50 + 2 x 25 8 Contactor MPPH - DU MCCB ACB 2000 x 1600 x 800
LTAPMH5001B2 500 3 x 100 + 3 x 50 + 2 x 25 8 Contactor MPPH - DU MCCB ACB 2000 x 1600 x 800

etaSYS - MH2 Standard APFC with a combination of Heavy Duty Capacitors, MCCB &
7% Detuned Reactor
Panel
Type of Main Dimension (mm)
Cat. Nos. Rating Step size (kVAr) Steps Switching Reactor
Branch
Device Capacitor Protection Incomer (H x W x D)*
(kVAr)
LTAPMH1002B2 100 50 + 25 + 15 + 5 + 5 5 Contactor MPPH 7% DU MCCB dsine MCCB 1600 x 1000 x 800
LTAPMH1252B2 125 2 x 12.5 + 2 x 25 + 50 5 Contactor MPPH 7% DU MCCB dsine MCCB 1600 x 1000 x 800
LTAPMH1502B2 150 2 x 12.5 + 3 x 25 + 50 6 Contactor MPPH 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMH1752B2 175 2 x 12.5 + 2 x 25 + 2 x 50 6 Contactor MPPH 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMH2002B2 200 2 x 12.5 + 1 x 25 + 3 x 50 6 Contactor MPPH 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMH2252B2 225 2 x 12.5 + 4 x 50 6 Contactor MPPH 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMH2502B2 250 2 x 25 + 4 x 50 6 Contactor MPPH 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMH2752B2 275 1 x 100 + 3 x 50 + 2 x 12.5 6 Contactor MPPH 7% DU MCCB dsine MCCB 2100 x 1200 x 800
LTAPMH3002B2 300 1 x 100 + 3 x 50 + 2 x 25 6 Contactor MPPH 7% DU MCCB dsine MCCB 2100 x 1200 x 800
LTAPMH3502B2 350 1 x 100 + 3 x 50 + 4 x 25 8 Contactor MPPH 7% DU MCCB dsine MCCB 2100 x 1400 x 800
LTAPMH4002B2 400 2 x 100 + 2 x 50 + 4 x 25 8 Contactor MPPH 7% DU MCCB ACB 2000 x 1600 x 1200
LTAPMH4502B2 450 2 x 100 + 4 x 50 + 2 x 25 8 Contactor MPPH 7% DU MCCB ACB 2000 x 1600 x 1200
LTAPMH5002B2 500 3 x 100 + 3 x 50 + 2 x 25 8 Contactor MPPH 7% DU MCCB ACB 2000 x 1600 x 1200

*Actual dimensions will be given in drawings

93
etaSYS - FH1 Standard APFC with a combination of Heavy Duty Capacitors & HRC Fuse
Panel Type of Dimension (mm)
Rating Step size (kVAr) Steps Switching Capacitor Reactor Branch Main
Cat. Nos. Protection Incomer (H x W x D)*
(kVAr) Device
LTAPFH0351B2 35 2 x 12.5 + 2 x 5 4 Contactor MPPH - HRCF dsine MCCB 1100 x 600 x 400
LTAPFH0501B2 50 2 x 12.5 + 2 x 10 + 1 x 5 5 Contactor MPPH - HRCF dsine MCCB 1100 x 600 x 400
LTAPFH0751B2 75 2 x 25 + 2 x 10 + 1 x 5 5 Contactor MPPH - HRCF dsine MCCB 1200 x 800x 400
LTAPFH1001B2 100 50 + 25 + 15 + 5 + 5 5 Contactor MPPH - HRCF dsine MCCB 1500 x 1000 x 500
LTAPFH1251B2 125 2 x 12.5 + 2 x 25 + 50 5 Contactor MPPH - HRCF dsine MCCB 1500 x 1000 x 500
LTAPFH1501B2 150 2 x 12.5 + 3 x 25 + 50 6 Contactor MPPH - HRCF dsine MCCB 1800 x 1000 x 600
LTAPFH1751B2 175 2 x 12.5 + 2 x 25 + 2 x 50 6 Contactor MPPH - HRCF dsine MCCB 1800 x 1000 x 600
LTAPFH2001B2 200 2 x 12.5 + 25 + 3 x 50 6 Contactor MPPH - HRCF dsine MCCB 1800 x 1000 x 600
LTAPFH2251B2 225 2 x 12.5 + 4 x 50 6 Contactor MPPH - HRCF dsine MCCB 1800 x 1000 x 600
LTAPFH2501B2 250 2 x 25 + 4 x 50 6 Contactor MPPH - HRCF dsine MCCB 1800 x 1000 x 600
LTAPFH2751B2 275 1 x 100 + 3 x 50 + 2 x 12.5 6 Contactor MPPH - HRCF dsine MCCB 2100 x 1200 x 600
LTAPFH3001B2 300 1 x 100 + 3 x 50 + 2 x 25 6 Contactor MPPH - HRCF dsine MCCB 2100 x 1200 x 600
LTAPFH3501B2 350 1 x 100 + 3 x 50 + 4 x 25 8 Contactor MPPH - HRCF dsine MCCB 2100 x 1200 x 600
LTAPFH4001B2 400 2 x 100 + 2 x 50 + 4 x 25 8 Contactor MPPH - HRCF ACB 2000 x 1600 x 800
LTAPFH4501B2 450 2 x 100 + 4 x 50 + 2 x 25 8 Contactor MPPH - HRCF ACB 2000 x 1600 x 800
LTAPFH5001B2 500 3 x 100 + 3 x 50 + 2 x 25 8 Contactor MPPH - HRCF ACB 2000 x 1600 x 800

etaSYS - FH2 Standard APFC with a combination of Heavy Duty Capacitors, HRC Fuse &
7% Detuned Reactor
Panel Type of Branch Main Dimension (mm)
Cat. Nos. Rating Step size (kVAr) Steps Switching Capacitor Reactor (H x W x D)*
(kVAr) Device Protection Incomer
LTAPFH1002B2 100 50 + 25 + 15 + 5 + 5 5 Contactor MPPH 7% HRCF dsine MCCB 1600 x 1000 x 800
LTAPFH1252B2 125 2 x 12.5 + 2 x 25 + 50 5 Contactor MPPH 7% HRCF dsine MCCB 1600 x 1000 x 800
LTAPFH1502B2 150 2 x 12.5 + 3 x 25 + 50 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFH1752B2 175 2 x 12.5 + 2 x 25 + 2 x 50 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFH2002B2 200 2 x 12.5 + 1 x 25 + 3 x 50 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFH2252B2 225 2 x 12.5 + 4 x 50 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFH2502B2 250 2 x 25 + 4 x 50 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFH2752B2 275 1 x 100 + 3 x 50 + 2 x 12.5 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1200 x 800
LTAPFH3002B2 300 1 x 100 + 3 x 50 + 2 x 25 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1200 x 800
LTAPFH3502B2 350 1 x 100 + 3 x 50 + 4 x 25 8 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1400 x 800
LTAPFH4002B2 400 2 x 100 + 2 x 50 + 4 x 25 8 Contactor MPPH 7% HRCF ACB 2000 x 1600 x 1200
LTAPFH4502B2 450 2 x 100 + 4 x 50 + 2 x 25 8 Contactor MPPH 7% HRCF ACB 2000 x 1600 x 1200
LTAPFH5002B2 500 3 x 100 + 3 x 50 + 2 x 25 8 Contactor MPPH 7% HRCF ACB 2000 x 1600 x 1200

etaSYS - FH3 Standard APFC with a combination of Heavy Duty Capacitors, Thyritor Switching
& 7% Detuned Reactor
Panel Type of Dimension (mm)
Rating Step size (kVAr) Steps Switching Capacitor Reactor Branch Main
Cat. Nos. Protection Incomer (H x W x D)*
(kVAr) Device
LTAPFH1003B2 100 50 + 25 + 15 + 5 + 5 5 Thyristor MPPH 7% HSF dsine MCCB 1800 x 1000 x 800
LTAPFH1253B2 125 2 x 12.5 + 2 x 25 + 50 5 Thyristor MPPH 7% HSF dsine MCCB 1800 x 1000 x 800
LTAPFH1503B2 150 2 x 12.5 + 3 x 25 + 50 6 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFH1753B2 175 2 x 12.5 + 2 x 25 + 2 x 50 6 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFH2003B2 200 2 x 12.5 + 1 x 25 + 3 x 50 6 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFH2253B2 225 2 x 12.5 + 4 x 50 6 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFH2503B2 250 2 x 25 + 4 x 50 6 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFH2753B2 275 1 x 100 + 3 x 50 + 2 x 12.5 6 Thyristor MPPH 7% HSF dsine MCCB 2200 x 1200 x 800
LTAPFH3003B2 300 1 x 100 + 3 x 50 + 2 x 25 6 Thyristor MPPH 7% HSF dsine MCCB 2200 x 1200 x 800
LTAPFH3503B2 350 1 x 100 + 3 x 50 + 4 x 25 8 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1600 x 800
LTAPFH4003B2 400 2 x 100 + 2 x 50 + 4 x 25 8 Thyristor MPPH 7% HSF ACB 2000 x 1600 x 1200
LTAPFH4503B2 450 2 x 100 + 4 x 50 + 2 x 25 8 Thyristor MPPH 7% HSF ACB 2000 x 1600 x 1200
LTAPFH5003B2 500 3 x 100 + 3 x 50 + 2 x 25 8 Thyristor MPPH 7% HSF ACB 2000 x 1600 x 1200
*Actual dimensions will be given in drawings
 94
etaSYS - MU1 Standard APFC with a combination of LTXL Capacitors & MCCB
Panel
Switching Type of Branch Main Dimension (mm)
Cat. Nos. Rating Step size (kVAr) Steps Reactor
Device Capacitor Protection Incomer (H x W x D)*
(kVAr)
LTAPMU1001B2 100 50 + 25 + 15 + 5 + 5 5 Contactor LTXL - DU MCCB dsine MCCB 1500 x 1000 x 700
LTAPMU1251B2 125 2 x 12.5 + 2 x 25 + 50 5 Contactor LTXL - DU MCCB dsine MCCB 1500 x 1000 x 700
LTAPMU1501B2 150 2 x 12.5 + 3 x 25 + 50 6 Contactor LTXL - DU MCCB dsine MCCB 1800 x 1000 x 700
LTAPMU1751B2 175 2 x 12.5 + 2 x 25 + 2 x 50 6 Contactor LTXL - DU MCCB dsine MCCB 1800 x 1000 x 700
LTAPMU2001B2 200 2 x 12.5 + 25 + 3 x 50 6 Contactor LTXL - DU MCCB dsine MCCB 1800 x 1000 x 700
LTAPMU2251B2 225 2 x 12.5 + 4 x 50 6 Contactor LTXL - DU MCCB dsine MCCB 1800 x 1000 x 700
LTAPMU2501B2 250 2 x 25 + 4 x 50 6 Contactor LTXL - DU MCCB dsine MCCB 1800 x 1000 x 700
LTAPMU2751B2 275 1 x 100 + 3 x 50 + 2 x 12.5 6 Contactor LTXL - DU MCCB dsine MCCB 2100 x 1200 x 700
LTAPMU3001B2 300 1 x 100 + 3 x 50 + 2 x 25 6 Contactor LTXL - DU MCCB dsine MCCB 2100 x 1200 x 700
LTAPMU3501B2 350 1 x 100 + 3 x 50 + 4 x 25 8 Contactor LTXL - DU MCCB dsine MCCB 2100 x 1200 x 700
LTAPMU4001B2 400 2 x 100 + 2 x 50 + 4 x 25 8 Contactor LTXL - DU MCCB ACB 2000 x 1600 x 1200
LTAPMU4501B2 450 2 x 100 + 4 x 50 + 2 x 25 8 Contactor LTXL - DU MCCB ACB 2000 x 1600 x 1200
LTAPMU5001B2 500 3 x 100 + 3 x 50 + 2 x 25 8 Contactor LTXL - DU MCCB ACB 2000 x 1600 x 1200

etaSYS - MU2 Standard APFC with a combination of LTXL Capacitors, MCCB &
7% Detuned Reactor
Panel
Switching Type of Branch Main Dimension (mm)
Cat. Nos. Rating Step size (kVAr) Steps Reactor
Device Capacitor Protection Incomer (H x W x D)*
(kVAr)
LTAPMU1002B2 100 50 + 25 + 15 + 5 + 5 5 Contactor LTXL 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMU1252B2 125 2 x 12.5 + 2 x 25 + 50 5 Contactor LTXL 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMU1502B2 150 2 x 12.5 + 3 x 25 + 50 6 Contactor LTXL 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMU1752B2 175 2 x 12.5 + 2 x 25 + 2 x 50 6 Contactor LTXL 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMU2002B2 200 2 x 12.5 + 1 x 25 + 3 x 50 6 Contactor LTXL 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMU2252B2 225 2 x 12.5 + 4 x 50 6 Contactor LTXL 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMU2502B2 250 2 x 25 + 4 x 50 6 Contactor LTXL 7% DU MCCB dsine MCCB 2100 x 1000 x 800
LTAPMU2752B2 275 1 x 100 + 3 x 50 + 2 x 12.5 6 Contactor LTXL 7% DU MCCB dsine MCCB 2100 x 1200 x 1200
LTAPMU3002B2 300 1 x 100 + 3 x 50 + 2 x 25 6 Contactor LTXL 7% DU MCCB dsine MCCB 2100 x 1200 x 1200
LTAPMU3502B2 350 1 x 100 + 3 x 50 + 4 x 25 8 Contactor LTXL 7% DU MCCB dsine MCCB 2100 x 1400 x 1200
LTAPMU4002B2 400 2 x 100 + 2 x 50 + 4 x 25 8 Contactor LTXL 7% DU MCCB ACB 2000 x 1800 x 1200
LTAPMU4502B2 450 2 x 100 + 4 x 50 + 2 x 25 8 Contactor LTXL 7% DU MCCB ACB 2000 x 1800 x 1200
LTAPMU5002B2 500 3 x 100 + 3 x 50 + 2 x 25 8 Contactor LTXL 7% DU MCCB ACB 2000 x 1800 x 1200

*Actual dimensions will be given in drawings

95
etaSYS - FU1 Standard APFC with a combination of LTXL Capacitors & HRC Fuse
Panel
Type of Main Dimension (mm)
Cat. Nos. Rating Step size (kVAr) Steps Switching Capacitor Reactor Branch
(H x W x D)*
(kVAr) Device Protection Incomer
LTAPFU1001B2 100 50 + 25 + 15 + 5 + 5 5 Contactor LTXL - HRCF dsine MCCB 1500 x 1000 x 700
LTAPFU1251B2 125 2 x 12.5 + 2 x 25 + 50 5 Contactor LTXL - HRCF dsine MCCB 1500 x 1000 x 700
LTAPFU1501B2 150 2 x 12.5 + 3 x 25 + 50 6 Contactor LTXL - HRCF dsine MCCB 1800 x 1000 x 700
LTAPFU1751B2 175 2 x 12.5 + 2 x 25 + 2 x 50 6 Contactor LTXL - HRCF dsine MCCB 1800 x 1000 x 700
LTAPFU2001B2 200 2 x 12.5 + 25 + 3 x 50 6 Contactor LTXL - HRCF dsine MCCB 1800 x 1000 x 700
LTAPFU2251B2 225 2 x 12.5 + 4 x 50 6 Contactor LTXL - HRCF dsine MCCB 1800 x 1000 x 700
LTAPFU2501B2 250 2 x 25 + 4 x 50 6 Contactor LTXL - HRCF dsine MCCB 1800 x 1000 x 700
LTAPFU2751B2 275 1 x 100 + 3 x 50 + 2 x 12.5 6 Contactor LTXL - HRCF dsine MCCB 2100 x 1200 x 700
LTAPFU3001B2 300 1 x 100 + 3 x 50 + 2 x 25 6 Contactor LTXL - HRCF dsine MCCB 2100 x 1200 x 700
LTAPFU3501B2 350 1 x 100 + 3 x 50 + 4 x 25 8 Contactor LTXL - HRCF dsine MCCB 2000 x 1600 x 1200
LTAPFU4001B2 400 2 x 100 + 2 x 50 + 4 x 25 8 Contactor LTXL - HRCF ACB 2000 x 1600 x 1200
LTAPFU4501B2 450 2 x 100 + 4 x 50 + 2 x 25 8 Contactor LTXL - HRCF ACB 2000 x 1600 x 1200
LTAPFU5001B2 500 3 x 100 + 3 x 50 + 2 x 25 8 Contactor LTXL - HRCF ACB 2000 x 1600 x 1200

etaSYS - FU2 Standard APFC with a combination of LTXL Capacitors, HRC Fuse &
7% Detuned Reactor
Panel Type of Dimension (mm)
Rating Step size (kVAr) Steps Switching Capacitor Reactor Branch Main
Cat. Nos. Protection Incomer (H x W x D)*
(kVAr) Device
LTAPFU1002B2 100 50 + 25 + 15 + 5 + 5 5 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFU1252B2 125 2 x 12.5 + 2 x 25 + 50 5 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFU1502B2 150 2 x 12.5 + 3 x 25 + 50 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFU1752B2 175 2 x 12.5 + 2 x 25 + 2 x 50 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFU2002B2 200 2 x 12.5 + 1 x 25 + 3 x 50 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFU2252B2 225 2 x 12.5 + 4 x 50 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFU2502B2 250 2 x 25 + 4 x 50 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1000 x 800
LTAPFU2752B2 275 1 x 100 + 3 x 50 + 2 x 12.5 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1200 x 1200
LTAPFU3002B2 300 1 x 100 + 3 x 50 + 2 x 25 6 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1200 x 1200
LTAPFU3502B2 350 1 x 100 + 3 x 50 + 4 x 25 8 Contactor MPPH 7% HRCF dsine MCCB 2100 x 1400 x 1200
LTAPFU4002B2 400 2 x 100 + 2 x 50 + 4 x 25 8 Contactor MPPH 7% HRCF ACB 2000 x 1600 x 1200
LTAPFU4502B2 450 2 x 100 + 4 x 50 + 2 x 25 8 Contactor MPPH 7% HRCF ACB 2000 x 1600 x 1200
LTAPFU5002B2 500 3 x 100 + 3 x 50 + 2 x 25 8 Contactor MPPH 7% HRCF ACB 2000 x 1600 x 1200

etaSYS - FU3 Standard APFC with a combination of LTXL Capacitors, Thyritor Switching &
7% Detuned Reactor
Panel Type of Dimension (mm)
Rating Step size (kVAr) Steps Switching Capacitor Reactor Branch Main
Cat. Nos. Protection Incomer (H x W x D)*
(kVAr) Device
LTAPFU1003B2 100 50 + 25 + 15 + 5 + 5 5 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFU1253B2 125 2 x 12.5 + 2 x 25 + 50 5 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFU1503B2 150 2 x 12.5 + 3 x 25 + 50 6 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFU1753B2 175 2 x 12.5 + 2 x 25 + 2 x 50 6 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFU2003B2 200 2 x 12.5 +1 x 25 + 3 x 50 6 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFU2253B2 225 2 x 12.5 + 4 x 50 6 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFU2503B2 250 2 x 25 + 4 x 50 6 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1000 x 800
LTAPFU2753B2 275 1 x 100 + 3 x 50 + 2 x 12.5 6 Thyristor MPPH 7% HSF dsine MCCB 2200 x 1200 x 1200
LTAPFU3003B2 300 1 x 100 + 3 x 50 + 2 x 25 6 Thyristor MPPH 7% HSF dsine MCCB 2200 x 1200 x 1200
LTAPFU3503B2 350 1 x 100 + 3 x 50 + 4 x 25 8 Thyristor MPPH 7% HSF dsine MCCB 2100 x 1600 x 1200
LTAPFU4003B2 400 2 x 100 + 2 x 50 + 4 x 25 8 Thyristor MPPH 7% HSF ACB 2000 x 1800 x 1200
LTAPFU4503B2 450 2 x 100 + 4 x 50 + 2 x 25 8 Thyristor MPPH 7% HSF ACB 2000 x 1800 x 1200
LTAPFU5003B2 500 3 x 100 + 3 x 50 + 2 x 25 8 Thyristor MPPH 7% HSF ACB 2000 x 1800 x 1200

*Actual dimensions will be given in drawings

 CAPACITOR STEP SIZE SELECTION GUIDELINES
IN APFC PANELS 96
Major part in the design of APFC panels is the selection of step size of capacitor banks and number of steps. The right
selection of step size and number of steps plays a significant role in the performance as well as cost of the APFC panel.
This section focuses on the need and ways of good step size (maximum and minimum sizes) selection and number of
steps.

1. Maximum Step Size Selection

The maximum capacitor rating in an APFC panel depends upon the following:
i. Maximum amount of load variation that happens in the industry at a time: Large load variations demand bigger
capacitor steps so that target power factor is achieved in short time, by less number of switching operations.

ii. Current and voltage transient withstand capabilities of the system:

• Current transients: Switching of big capacitors (usually above 100 kVAr) introduces large magnitude of inrush
current (current transients) for a small duration. This results in high thermal and electrical stress on capacitors,
short circuit protection devices and mainly, the switching device. This may lead to their nuisance tripping and
premature failures
• Voltage transients: Switching of big capacitors may cause transient over voltages, which might result in failure
of sensitive electronic devices

Thus, the maximum size of the capacitor step is a trade-off between the points i and ii. Practically acceptable
maximum possible rating in any APFC panel shall be 100 kVAr. If this 100 kVAr rating capacitor is switched using
power contactor, the peak inrush current may reach as high as 75 kA. Hence, the capacitors should be switched
using either capacitor duty contactors or thyristor switching module.

However, thyristor switching module or capacitor duty contactor for 100 kVAr rating is not readily available. Hence,
the best way to switch a 100 kVAr bank is by connecting two 50 kVAr TSM / contactor in parallel, each with a
separate physical 50 kVAr capacitor banks. The control supply to both the 50 kVAr TSM/contactors shall be common
(one relay output of the controller), so that both of the devices are triggered at the same time. To achieve this, the
common output of the APFC relay should be programmed as 100 kVAr. Hence, physically they are two separate 50
kVAr banks, whereas electrically they behave as a single 100 kVAr bank.

A sample connection diagram for switching a step of 100 kVAr capacitor using two 50 kVAr capacitor duty
contactors / TSM is shown as under:

MCCB for MCCB for

50 kVAr 50 kVAr

MO C MO C
contactor / contactor /
TSM TSM
50 kVAr 50 kVAr

Common control supply

7% Detuned 7% Detuned
etaCON Reactor Reactor
APFC Controller 50 kVAr 50 kVAr

Capacitor Capacitor
60 kVAr 480 V 60 kVAr 480 V

Figure 1: Connection diagram showing switching logic of 100 kVAr bank

97
2. Minimum Step Size Selection
The minimum capacitor rating depends on how precise the power factor needs to be maintained. This minimum
kVAr rating depends upon the minimum current sensitivity (typically around 2.5%) of the APFC controller. However
the change in PF due to these minimum selected kVAr rating would be usually in the 3rd or 4th decimal places
(depending on panel size or kVAr requirement), whereas the electricity board is concerned only with the first two
digits of PF (like 0.99).
Typically many industries want the desired target PF to be unity (exactly 1.00), in order to get incentives from some
EBs. But practically, the optimum target PF has to be 0.96 to 0.99. These are healthy levels of power factor as it will
have safety margin that avoids the leading power factor as well as any dangerous harmonic amplification (due to
more capacitance in the system).
Hence, as a rule of thumb, the minimum kVAr rating in an APFC panel can be chosen to be 5-10% of overall rating of
APFC panel. For smaller rating APFC panels (up to 100 kVAr), the smallest step can be 5 kVAr and for bigger rating
APFC panels (above 600 kVAr and up to 1000 kVAr) the minimum rating can be 25 kVAr.

3. Number of Steps / Branches in APFC Panels

Once the minimum and maximum kVAr rating of the APFC panel is selected, the number of branches can be decided
upon based of the following:
I. Technology of APFC controllers: Latest APFC controllers like etaCON L Series employ self-optimized intelligent
switching where the controller calculates the exact kVAr requirement and switches ON / OFF the appropriate
capacitors irrespective of the capacitors already in circuit. Traditional controllers employing linear or circular
switching require more number of smaller steps (like 1:2:2:…) for effective power factor correction. Whereas
the latest controllers like etaCON can have a mix of large and small steps reducing the number of steps in
capacitor bank as well as the cost of associated switchgear.
ii. Size & cost of APFC panel: More the number of steps more will be the cost of APFC panel, due to more number of
switchgear, bigger size of panel and others.

An APFC panel should have:

a. Maximum number of electrical steps (combination of physical steps) to ensure more accurate and flexible
power factor correction
b. Minimum number of physical steps to reduce the size and cost of the panel

Let us consider a few examples of step size selection in APFC panels.

I. 100 kVAr APFC panel Case A Case B

Step configuration 10 + 10 + 10 + 10 + … 10 times 50 + 25 + 15 + 5 + 5
Step resolution 10 kVAr 5 kVAr
Electrical Steps 10, 20, 30, 40, 50, … 100 5, 10, 15, 20, 25, 30, … 100
Physical Steps 10 5
No. of Electrical Steps 10 20
In case B, 20 electrical steps are possible with only 5 physical steps; whereas in case A, 10 physical steps are required
to achieve 10 electrical steps.

II. 300 kVAr APFC panel Case A Case B

Configuration 25 + 25 + 25 + 25 + … 12 times 1x100 + 3x50 + 2x25
Step resolution 25 kVAr 25 KVAr
Electrical Steps 25, 50, 75, 100, 125, … 275, 300 25, 50, 75, 100, 125, … 275, 300
Physical Steps 12 6
No. of Electrical Steps 12 12
Case B is better as same electrical steps are achieved with just 6 physical steps.

III. 600 kVAr APFC panel Case A Case B

Configuration 50 + 50 + 50 + 50 + … 12 times 3x100 + 5x50 + 2x25
Step resolution 50 kVAr 25 KVAr
Electrical Steps 50, 100, 150, 200, 250, … 600 25, 50, 75, 100, 125, … , 600
Physical Steps 12 10
No. of Electrical Steps 12 24
In Case B, 24 electrical steps are possible with only 10 physical steps; whereas in Case A, 12 physical steps are required
to achieve 12 electrical steps.
 98
Summary
• APFC panels with more number of steps (more than 12) does not always mean better step resolution
• With the latest APFC controller technology, fewer steps are sufficient to achieve better step resolution and control
of power factor
• Hence, usually a combination of large, small and very small ratings is used in steps of capacitor banks, as given
below:
1. Large rating capacitors (100 kVAr maximum) are required to PF compensation of base load and coarse power
factor compensation
2. Medium rating capacitors are meant for variable part of the reactive power compensation.
3. Small rating capacitors (usually 5 to 10% of total kVAr or 25 kVAr for panels above 500 kVAr) are meant for fine
tuning of the power factor.

Considering the above points, following table suggests optimum number of steps and step sizes from 35 kVAr to
1000 kVAr. Beyond 1000 kVAr, it is always better to split the APFC panels and install them at different PCC/MCC
levels.

Panel No. of No. of

Electrical / Logical Steps
Rating Physical Step Size (kVAr) Physical Electrical
(all possible combination of physical steps )
(kVAr) Steps Steps

35 2x12.5 + 2x5 4 5, 10, 12.5, 17.5, 22.5, 25, 30, 35 8

50 2 x 12.5 + 2x10 + 1x5 5 5, 10, 12.5, 15, 17.5, 20, 22.5, 25, 27.5, 30, 35, 37.5, 40, 45, 50 15
75 2 x 25 + 2x10 + 1x5 5 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, … 70, 75 15
100 50 + 25 + 15 + 5 + 5 5 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, …95,100 20
125 2 x 12.5 + 2 x 25 + 50 5 12.5, 25, 37.5, 50, 62.5, 75, 87.5, 100, 112.5, 125 10
150 2 x 12.5 + 3 x 25 + 50 6 12.5, 25, 37.5, 50, 62.5, 75, 87.5, … 137.5, 150 12
175 2 x 12.5 + 2 x 25 + 2 x 50 6 12.5, 25, 37.5, 50, 62.5, 75, 87.5, … 162.5, 175 14
200 2 x 12.5 + 25 + 3 x 50 6 12.5, 25, 37.5, 50, 62.5, 75, 87.5, … 187.5, 200 16
225 2 x 12.5 + 4 x 50 6 12.5, 25, 37.5, 50, 62.5, 75, 87.5, … 121.5, 225 18
250 4 x 50 + 2 x 25 6 25, 50, 75, 100, 125, 150, 175, 200, 225, 250 10
275 5 x 50 + 1 x 25 6 25, 50, 75, 100, 125, 150, 175, 200, … 250, 275 11
300 1 x 100 + 3 x 50 + 2 x 25 6 25, 50, 75, 100, 125, 150, 175, 200, … 275, 300 12
350 1 x 100 + 3 x 50 + 4 x 25 8 25, 50, 75, 100, 125, 150, 175, 200, … 325, 350 14
400 2 x 100 + 2 x 50 + 4 x 25 8 25, 50, 75, 100, 125, 150, 175, 200, … 375, 400 16
450 2 x 100 + 4 x 50 + 2 x 25 8 25, 50, 75, 100, 125, 150, 175, 200, … 425, 450 18
500 3 x 100 + 3 x 50 + 2 x 25 8 25, 50, 75, 100, 125, 150, 175, 200, … 475, 500 20
550 3 x 100 + 3 x 50 + 4 x 25 10 25, 50, 75, 100, 125, 150, 175, 200, … 525, 550 22
600 3 x 100 + 5 x 50 + 2 x 25 10 25, 50, 75, 100, 125, 150, 175, 200, … 575, 600 24
650 4 x 100 + 4 x 50 + 2 x 25 10 25, 50, 75, 100, 125, 150, 175, 200, … 625, 650 26
700 3 x 100 + 5 x 50 + 6 x 25 12 25, 50, 75, 100, 125, 150, 175, 200, … 675, 700 28
750 5 x 100 + 3 x 50 + 4 x 25 12 25, 50, 75, 100, 125, 150, 175, 200, … 725, 750 30
800 5 x 100 + 5 x 50 + 2 x 25 12 25, 50, 75, 100, 125, 150, 175, 200, … 775, 800 32
850 6 x 100 + 4 x 50 + 2 x 25 12 25, 50, 75, 100, 125, 150, 175, 200, … 825, 850 34
900 7 x 100 + 2 x 50 + 4 x 25 12 25, 50, 75, 100, 125, 150, 175, 200, … 875, 900 36
950 8 x 100 + 2 x 50 + 4 x 25 12 25, 50, 75, 100, 125, 150, 175, 200, … 925, 950 38
1000 9 x 100 + 1 x 50 + 2 x 25 12 25, 50, 75, 100, 125, 150, 175, 200, … 975, 1000 40
The above table is for illustration only, which may be applicable for majority of industries. For accurate compensation, step ratings
shall be decided after studying the load profile of the industry.

Disclaimer
For accurate compensation, the load profile of the industry needs to be studied. This gives an indication of the size of
peak loads, base loads, possible harmonics, power factor and thus, helps determine step sizes based on load
variations. In some cases, the load requirements can also be established from equipment lists.
99 FUSE SELECTION FOR APFC PANELS
For any APFC panel, fuses are required for faster short circuit protection and overload protection of capacitors. Fuse
selection for capacitive load is critical because of heavy inrush current, high overload capacity and continuous full
load. These inherent traits of a capacitor, complicates the selection process. Hence the selection should be such that
even during these permissible abnormalities, the fuse should not blow.

Normally, the maximum permissible current in a capacitor branch is 2 times the rated current. This factor is comprised
of the following:

• Harmonics overload and over voltage - 30%

• Capacitance tolerance -10%
• Frequency variation - 2%
• Fuse deration factor - 35%

The fuse used for branch protection must be capable of carrying this current continuously. Hence the fuse should be
sufficiently rated so as to avoid the deterioration of the fuse element. Further the fuse should not blow during
switching of the capacitors because of the inrush current (more than100 times the capacitor rated current). In order
to prevent nuisance operation of fuse, its time-current characteristic should cover the peak inrush current of the
capacitor. Hence for the optimal selection of fuses, the inrush current must be limited by using either capacitor duty
contactor or inrush current limiting reactor.

The following table** shows the selection of Fuses and Capacitor switching contactors for an APFC panel:

Allowed O/C for Recommended Fuse Rating

kVAr Rated Current* (A) Derating Factor
Capacitor (A) Contactor* (A)

10 13.12 2 26.24 MO C12.5 32

15 19.68 2 39.36 MO C15 40
20 26.24 2 52.48 MO C20 63
25 32.80 2 65.60 MO C25 80
50 65.61 2 131.22 MO C50 160

* Selection principle is same for other family of fuses

** The table is valid only for L&T switchgear and capacitors at 440 V

The rated current of a capacitor can be calculated as.

(1000 x kVAr)
( 3 x V)

For any capacitor bank, permissible overload is 2 times rated capacitor current. Hence, fuses should be rated to carry
continuous overcurrent as given in the above table. In case Thyristor Switching Modules are used instead of capacitor
duty contactors, it is highly recommended to use High Speed Fuses (semiconductor fuse).

Above selection chart is valid only if fuses are used along with capacitor duty contactor. Please consider the above
table purely as a guideline for selection. Actual selection needs to be done based on considerations of connected load
and the electrical network properties.
 MCCB SELECTION FOR APFC PANELS 100
For any APFC panel, MCCBs are required for short circuit protection, overload protection and for isolation of
capacitors. MCCB selection for capacitive load is tricky because of heavy inrush current, high overload capacity and
continuous full load. These inherent traits of a capacitor, complicates the selection process. The selection should be
such that the MCCB should not nuisance trip during inrush current and should withstand continuous flow of
overload current.

Whenever we use MCCB in an APFC panel, proper measures need to be taken against the ill effects of the inrush
current. Normally the inrush current (more than100 times the capacitor rated current) will remain for a few micro-
seconds and will not be sensed by the MCCB. However the contacts of MCCB may repel and bounce because of the
current limiting feature, causing micro-arcs between the contacts of MCCB. This multiple bounce can result in
premature failure of MCCB contacts. In order to reduce the magnitude of the peak inrush current, MCCBs must be
used along with capacitor duty contactors or inrush current limiting reactors.

The maximum permissible current in a capacitor branch is 1.46 times the rated current. This factor is comprised of the
following:

• Harmonics overload and over voltage - 30%

• Capacitance tolerance - 10%
• Frequency variation - 2%

The branch MCCB must be capable of carrying this current continuously.

The following table** shows the selection of MCCBs and Capacitor switching contactors for an APFC panel:

Permissible Thermal Setting (A) Magnetic

Rated Derating Recommended
kVAr Capacitor MCCB* Setting
Current*A Factor Contactor+ IR
O/L (A) IN (6 to 10*IR)
(100% IN)
10 13.12 1.46 19.16 MO C12.5 DH / DU / DN 19 19 171
15 19.68 1.46 28.74 MO C15 DH / DU / DN 29 29 261
20 26.24 1.46 38.32 MO C20 DH / DU / DN 38 38 342
25 32.80 1.46 47.90 MO C25 DH / DU / DN 48 48 432
30 39.37 1.46 57.47 MO C30 DH / DU / DN 58 58 513
50 65.61 1.46 95.79 MO C50 DH / DU / DN 96 96 864

* Selection principle is same for other family of MCCBs

**The table is valid only for L&T switchgear and capacitors at 440 V

The rated current of a capacitor can be calculated as

(1000 x kVAr)
( 3 x V)
For any capacitor bank, permissible overload is 1.46 times rated capacitor current. Hence, MCCB should be rated to
carry continuous over current as given in the above table.

Above selection chart is valid only if MCCB is used along with capacitor duty contactor Please consider the above
table purely as a guideline for selection. Actual selection needs to be done based on considerations of connected load
and the electrical network properties.
101 CABLE SELECTION FOR CAPACITORS
Switchgear and cable selection for capacitor application is quite challenging. The reason is the capacitive networks
are more prone to over-current, high peak inrush current and continuous flow of full load current. Usually the
capacitors are designed to withstand and operate normally, even during the above said abnormalities, for a finite
amount of time. Hence, the switchgear and cables in the capacitor network should be rated accordingly, so as to
withstand & operate normally during these abnormalities.

The capacitors draw over-current because of the harmonics, capacitance tolerances, voltage variation and frequency
variation. The permitted over-current is up to 146% of the rated current, which comprises the following:

• Harmonics overload and over voltage – 30%

• Capacitance tolerance – 10%
• Frequency variation – 2%

Accordingly, the cables should also be derated, to continuously withstand permitted over-current. The derated cable
will also help in withstanding the electrical and thermal stresses that occur during every switching cycle because of
high inrush current.

Following is the recommended cable selection chart:

Current at the Rated Derated Current at the Minimum Recommended

Capacitor Voltage (in A) Rated Voltage (in A) Copper Cable Size**
Rating (kVAr)
(sq.mm)
440 V 415 V 440 V 415 V
1 1.31 1.39 1.92 2.03 0.5
2 2.62 2.78 3.83 4.06 0.5
3 3.94 4.17 5.75 6.09 0.75
4 5.25 5.56 7.66 8.12 1
5 6.56 6.96 9.58 10.16 1
6 7.87 8.35 11.49 12.19 2.5
7.5 9.84 10.43 14.37 15.23 2.5
8.3 10.89 11.55 15.90 16.86 2.5
10 13.12 13.91 19.16 20.31 4
12.5 16.40 17.39 23.95 25.39 4
15 19.68 20.87 28.74 30.47 6
20 26.24 27.82 38.32 40.62 10
25 32.80 34.78 47.90 50.78 16
50 65.61 69.56 95.79 101.56 35
75 98.41 104.34 143.69 152.34 70
100 131.22 139.12 191.58 203.12 95

**Cross section values mentioned above are guidelines that are valid for operation under normal conditions and at ambient
temperature of 40°C.

Busbar selection in APFC panels can be done with the standard calculations for short circuit withstand capability and
temperature rise (current density). The only assumption is that the rated current should be considered as 146% of the
total capacitor rated current.

It is recommended to use capacitor duty contactors to reduce the magnitude of peak inrush current. This will reduce
the thermal and electrical stress in the capacitors, cables and switchgear, which happens during each switching cycle.
This also prevents the premature failure of capacitors and nuisance tripping of short circuit protection device. The
above special selection for cables will also overcome the heating and losses that happen because of skin effect.
 THERMAL DESIGN OF APFC PANELS 102
The life of the power capacitors and other equipment in APFC panels depend very much on the operating
temperature. In panels with detuned harmonic filter reactors and thyristor switches, the chances of elevated
temperature are high, as these equipments generate relatively more heat.
Hence in order to maximise the life of the capacitors and other important equipments in the APFC panel, the
temperature must not be allowed to increase beyond certain limit. This article briefs some guidelines about the
thermal design of APFC panels and thereby managing the heat effectively.

For any panel, the temperature rise can be reduced by the following three ways:
n Operating at lower ambient temperature
n Using devices with lower power loss
n Dissipating the excess heat, so that temperature rise is controlled

There is minimal control over the first two conditions. But the third condition completely depends upon the design of
the panel. By offering effective cooling methods, the excess heat generated by the equipments can be dissipated.
Selection of the cooling methods can decided based on the internal temperature rise inside the panel. The maximum
internal temperature can be calculated using the following formula:

Pd
Internal Temperature (Ti ) = + Ta
kxS

Where, Pd = Total power dissipated in the panel (in watts)

k = constant defined by the material used to manufacture the enclosure
For painted sheet-steel enclosure, k = 5.5 W/m2 °C
S = effective surface area of the panel (in m2)
Ta = Ambient temperature (in °C)

If the temperature rise (Ti – Ta) is within the acceptable limits, natural cooling would be sufficient; else forced cooling
method should be employed for dissipating excessive heat.

1. Natural Cooling
In most of PCCs and MCCs, the temperature rise remains under desirable limits with natural circulation of air
(through natural convection and radiation). The air circulation happens through some slots in the enclosure, called
the louvers. When temperature rises inside the panel, the pressure of the air increases and the density reduces.
Hence the hot air tends to move upwards. The hot air would go out through the louvers provided at the top side of
the panel. Fresh cold air would enter the panel through the louvers provided at the bottom. This is represented in
Figure 1.

Figure 2 represents the common usage of extra louvers in-between the top and bottom louvers.
The common misconception behind this is that, extra louver would increase the volume of air flow. Practically, this
does not happen because the volume of the panel is fixed.
This results in the reduced air flow at the bottom section of the panel, as some air enters through the middle louvers.
Hence, the temperature of the lower section of the panel will be higher than the upper section.
103
It is recommended to follow the panel design as per the Figure 1.

SIDE VIEW SIDE VIEW

LOUVERS LOUVERS

Hotl Air Outlet

Reduced rate
of air flow,
hence, over
Cool Air Inlet heating

PLINTH PLINTH

Figure 1 Figure 2

2. Forced Cooling
In most of the APFC panels and in some MCC and PCC panels, the above method would not offer sufficient cooling.
In order to maintain the desired temperature levels (ambient temperature + allowed temperature rise), forced
cooling methods (using fans at the top) should be employed, which would increase the rate of air flow.
In Figure 3 the cold air enters through the bottom louvers, flows through all the equipments and they are forced out
of the panel through fans. Hence, temperature rise in the panel is kept under check and there are no hot
spots/sections.
In Figure 4 provision of additional louvers, actually disturbs the uniformity of the flow. Major chunk of cold air would
enter through the top louver and result in “short cycling”. So the bottom section of the panel would see higher
temperature rise.

SIDE VIEW SIDE VIEW

LOUVERS
Hotl Air Outlet
Forced out via Fan

Reduced rate
of air flow,
hence, over
Cool Air Inlet heating

PLINTH PLINTH

Figure 3 Figure 4
 104
2.1 Fan Selection for Forced Cooling
3
Fan selection is based on the rate of air flow, which is measured in m /h or Cubic Feet per Minute (CFM), where
1 CFM = 1.7 x 1 m3/h. Following is the formula to calculate air flow rate:

P d - [k x S (T d - T a )]
Q = Cx
(T d - T a )

Where,
Q = Air flow rate (in m3/h)
C = Coefficient related to the altitude above the sea level

Altitude (in meters) C

0 to 100 3.1

101 to 250 3.2

251 to 500 3.3

501 to 750 3.4

751 to 1000 3.5

Pd = total power loss (watts) inside the panel, by summing up the power loss of individual
devices like capacitors, reactors, thyristor switches, contactors,
bus bars, joints and so on.
k = constant defined by the material used to manufacture the enclosure.
2 O
For painted sheet-steel enclosure, k = 5.5 W/m C
S = Open surface area of the panel (in sq. m) can be calculated using one of the below formulas:

Formula for Calculating S (in sq. m)

Position of the Enclosure as per IEC 890

accessible on all sides S = 1.8 x H x (W + D) + 1.4 x W x D

placed against a wall S = 1.4 x W x (H + D) + 1.8 x D x H

end of a row of enclosures S = 1.4 x D x (H + W) + 1.8 x W x H

end of a row of enclosures with back

S = 1.4 x H x (W + D) + 1.4 x W x D
against the wall

intermediate in a row of enclosures S = 1.8 x W x H + 1.4 x W x D + D x H

intermediate in a row of enclosures with

S = 1.4 x W x (H + D) + D x H
the back against the wall

intermediate in a row of enclosures back

S = 1.4 x W x H + 0.7 x W x D + D x H
against the wall with top part covered

Td = Desired Maximum temperature inside the enclosure

Ta = Ambient temperature
105
This is a simple method of thermal management and fan selection, which is suitable for majority of the panels. At the
same time, some other aspects like position of mounting various equipments in the APFC panel should be taken care.
Some of them are as follows:
n Capacitors should be kept below the reactors, which are the major heat sources. This is because the elevated
temperature would reduce the life of the capacitors.
n The reactors should be mounted in the zigzag position (as shown in the below figure), in order to ensure better
heat flow. If the reactors are kept one above other, the bottom most reactors would heat up the other reactors that
are mounted above them.
n Thyristor switching modules should be mounted vertically (position of heat sink should be parallel to the air flow
direction) and in zigzag positions. The TSM panel should be non-compartmentalized design for better heat
dissipation.
n Reactors & capacitors should be mounted over channels to allow the free flow of air. Flat base plates are not
recommended.
n The panel should not be compartmentalized. Compartmentalised design would lead to heat accumulation in the
panel.
n For Reactors and TSM, a clearance of 100 mm should be maintained in all directions.

50 kVAr 50 kVAr

50 kVAr 50 kVAr

Zig-zag arrangement
of reactors

Reactors
25 kVAr 25 kVAr 7% Detuned

Capacitors 480V
Capacitors kept
below the major
30 30 30 30 30 30 30 30
heat source
kVAr kVAr kVAr kVAr kVAr kVAr kVAr kVAr (reactors)

PLINTH

Hence, in APFC panels, a proper thermal design would pave way for maximising the life of important equipments like
capacitors, thyristor switches, reactors and other switchgear.
 etaPRO v2.3 - MULTI UTILITY SOFTWARE PACKAGE 106

etaPRO is an innovative, multi-utility and user friendly software package, related to Reactive Power Management. The
users will get the benefit of easy and error free selection of products.

Features

KVAR
n CALCULATION
Easy calculation of capacitor kVAr rating
if initial power factor and final power
factor are known

DETUNED
n HARMONIC FILTER
SELECTION
Selection of right capacitor-reactor
combination (detuned harmonic filter)
and the catalogue numbers

PAYBACK
n CALCULATION
Monthly payback calculation, after
improving the power factor to the
desired level
107

APFC
n PANEL BILL OF MATERIALS GENERATION
Generation of bill of materials, covering capacitor
selection, switchgear selection, switching device
selection. The output gives the catalogue numbers
and MRP of all the items in the panel, that can be
exported to excel format.
Ø BoM generation up to 1400 kVAr APFC Panels
with maximum 14 steps
Ø Auto-calculation of rated incomer and branch
currents
Ø Switchgear selection options for main incomer
(ACB, MCCB and SDF) and branch protection
(MCCB, SDF, HRC Fuse and MCB)
Ø Accessories selection for the selected switchgear
Ø Capacitors and reactor selection
Ø Instant catalogue access for selected
switchgear/capacitors
Ø Final BoM in two forms:
l Branch-wise list of items
l Consolidated list of items

TECHNICAL
n ARTICLES AND PRESENTATIONS
Technical articles related to Power Quality Solutions

Benefits
End customers and panel builders will be benefitted by the following ways:
Easy
n selection of capacitors and reactors
n Error free switchgear ratings selection
n Time saving while preparing APFC quotations
n Optimum step size selection
n Automatic selection of capacitor-reactor combinations
n BoM can be exported to Microsoft Excel format

For download, visit www.LNTEBG.com/etaPRO

Aimed at maximizing productivity, conserving energy, minimizing costs and enhancing safety, our Electrical
& Automation training programmes have benefitted over 1.77 Lakh professionals in the last 30 years. These
training programmes are highly beneficial as they provide right exposure and impart knowledge on
selection, installation, maintenance and testing of Electrical & Automation Products.

So gain the advantage and go the extra mile with:

— 14 courses on contemporary topics
— Courses applicable to all switchgear brands
— Training Centers in Pune, Lucknow, Coonoor, Vadodara, Delhi & Kolkata
— Blend of theory and practical experience

The typical training programmes cover:

— Low Voltage & Medium Voltage Switchgear
— Switchboard Electrical Design
— AC Drives & Building Management Solutions
— Protective Relays & Earthing
— Power Quality Solutions

Please contact any of the training centres for participation and detailed training programme schedule.

Pune Lucknow Coonoor

Larsen & Toubro Limited Larsen & Toubro Limited Larsen & Toubro Limited
Switchgear Training Centre, Switchgear Training Centre, Switchgear Training Centre,
T-156/157, MIDC C - 6 & 7, UPSIDC Ooty-Coonoor Main Road
Bhosari, P. O. Sarojininagar, Yellanahalli P.O.,
Pune - 411 026 Lucknow - 226 008 The Nilgiris - 643 243
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Vadodara Delhi Kolkata

Larsen & Toubro Limited Larsen & Toubro Ltd Larsen & Toubro Limited
Switchgear Training Centre Switchgear Training Centre Switchgear Training Centre
Behind L&T Knowledge City, 32, Shivaji Marg, 4th Floor, 3B, Shakespeare Sarani,
Near Village Ankhol, Near Motinagar Metro Station, Kolkata - 700071
Vadodara - 390019 New Delhi - 110015 Tel: 033 42005975 / 42005978
Tel: 0265 2457805 Tel: 011 41419515 / 41419695 / 41419500 E-mail: stc-kolkata@Lntebg.com
E-mail: stc-vadodara@Lntebg.com Fax: 011 41419600
E-mail: stc-delhi@Lntebg.com
 Electrical Standard Products (ESP) Offices:

HEAD OFFICE Khairasol, Degaul Avenue L&T Business Park,

L&T Business Park, Durgapur 713 212 Tower 'B' / 3rd Floor
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Product improvement is a continuous process. For the latest information and special applications, please contact any of our offices listed here.

Larsen & Toubro Limited, Electrical Standard Products

Powai Campus, Mumbai 400 072

Customer Interaction Center (CIC)

BSNL / MTNL (toll free) : 1800 233 5858 Reliance (toll free) : 1800 200 5858
Tel : 022 6774 5858,
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Registered Office: L&T House, N. M. Marg, Ballard Estate, Mumbai 400 001, INDIA CIN: L99999MH1946PLC004768 SP 50481 R5