1.
Loads have PF
2. What is PF
3.PFC Types
4. PFC location
5. PFC sizing
PFC description
C.B of PFC
ACTIVE & REACTIVE POWERS
Most plant loads are Inductive and require a magnetic field to
operate:
Motors
Transformers
Florescent lighting
The magnetic field is necessary, but produces no useful work
The utility must supply the power to produce the magnetic field
and the power to produce the useful work: You pay for all of it!
These two types of current are the ACTIVE and REACTIVE
components
Examples of Electric Equipment and Their Power Factor
Different types of electric equipment have different Power Factors and
consequently different efficiencies and current requirements:
Name of Equipment Power Factor Percent
Lightly loaded induction .20
motor
Loaded induction motor .80
Neon-lighting equipment .30 - .70
Incandescent lamps 1
All types of resistance heating 1
devices (e.g. toaster, space
heater)
6
Typical Uncorrected Power Factor
(Use only as a Guide)
By Industry Power By Operation Power
Factor Factor
Auto parts 75-80 Air compressor:
Brewery 76-80 External motors 75-80
Cement 80-85 Hermetic motors 50-80
Chemical 65-75 Metal working:
Coal mine 65-80 Arc welding 35-60
Clothing 35-60 Arc welding with 40-60
standard capacitors
Electroplating 65-70 Resistance welding 40-60
Foundry 75-80 Machining 40-65
Forge 70-80 Melting:
Hospital 75-80 Arc furnace 75-90
Machine 60-65 Inductance furnace 100
manufacturing 60Hz
Metalworking 65-70 Stamping:
Office building 80-90 Standard speed 60-70
Oil-field pumping 40-60 High speed 45-60
Paint 55-65 Spraying 60-65
manufacturing
Plastic 75-80 Weaving:
Stamping 60-70 Individual drive 60
Steelworks 65-80 Multiple drive 70
Textile 65-75 Brind 70-75
Tool, die, jig 60-65
From IEEE Std 141-1993
1. Loads have PF
2. What is PF
3.PFC Types
4. PFC location
5. PFC sizing
PFC description
C.B of PFC
Why do we install Capacitors?
Before After In this example, demand
was reduced to 8250 kVA
from 10000 kVA.
1750KVA Transformer
Capacity Release.
The power factor was
improved from 80% to 97%
1. Loads have PF
2. What is PF
3.PFC Types
4. PFC location
5. PFC sizing
PFC description
C.B of PFC
POWER FACTOR CORRECTION METHODS
Fixed Capcitors
Switch Capacitors
11
Fixed Capacitors - Low Voltage
Main Benefit
pf correction
Side Benefit
voltage support
Small I2R reduction
Usage
Correcting pf on individual loads such as
motors
Disadvantages
Overcompensation (correct past unity)
Not to be used on non-linear loads
Unable to track minute by minute load
changes occurring on non-compensated
feeders
Electronic Switch –Transient Free
L1 L2 L3
Fuses
SCR-Diode
De-tuned
Inductor
1. Loads have PF
2. What is PF
3.PFC Types
4. PFC location
5. PFC sizing
PFC description
C.B of PFC
Capacitor Locations
Three Options for Applying Power Factor
Capacitors:
A) Fixed capacitors @ individual motors or @ MCC
B) Automatic Banks at Main Switch Board
C) De-tuned Automatic Capacitor Bank at Main Switch
Board
Harmonic
Source
e.g. Variable
M M M M M Speed Drive
A B C A
1. Loads have PF
2. What is PF
3.PFC Types
4. PFC location
5. PFC sizing
PFC description
C.B of PFC
Power Factor1=74%
Actual Power=594 kw
Interested to boost up=97% ,Power
Factor2=97%
Power Factor=KW/KVA
Cos = kW / kVA
= Cos-1 (PF1)
= Cos-1 (74%) =42.27 o
21
The reactive power was about:
Tan = kVAr / kW
kVAr = kW x tan
kVAr = 594 kW x tan (42.27) = 540 kVAr
If the power factor were increased to 97%, the reactive
power would be about:
Cos = kW / kVA
= Cos-1 (PF2)
= Cos-1 (97%) = 14.07 o
kVAr = kW x tan
kVAr = 594 kW x tan (14.07) = 149 kVAr
22
Thus, the amount of capacitance required
to boost power factor from 74% to 97% :
540 kVAr – 149 kVAr = 391 kVAr
So I recommended 400kvar
23
1. Loads have PF
2. What is PF
3.PFC Types
4. PFC location
5. PFC sizing
PFC description
C.B of PFC
PFC
Description
KVAR No. of steps Delta
PFC
Description
KVAR No. of steps Delta
Standard Design of P.F.C:
1.Fixed Value of 50KVAR.
2.Variable Values may be :[12.5-20-25-50…]
3.Steps may be: [10-12-16…]
For Example:
If Qc=350KVAR
Qc= 50 + 12 x 25
Fixed Steps Variable
1. Loads have PF
2. What is PF
3.PFC Types
4. PFC location
5. PFC sizing
PFC description
C.B of PFC
C.B Rating:
Ic.b= 1.1 x 1.3 x Icapacitor.
1.3: 30% increasing due to Harmonics.
1.1: 10% increasing due to tolerance
Icapacitor= 1.52 Scap(KVAR) For 400V.
Ic.b= 1.1 x 1.3 x 1.52 Scap(KVAR) .
Ic.b=2x Scap(KVAR).
35
