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EASTERN RAILWAYS,HOWRAH
INDIAN RAILWAYS
PROJECT REPORT ON TRAINING AT D.E.E.(GENERAL) UNDER THE
GUIDANCE OF A.E.E.(G)/HWH , EASTERN RAILWAY,HOWRAH
SUMMER TRAINING 2014



Submitted by-
PiyushRanjan,
2
nd
year undergraduate,
Dept. of Electrical and Electronics,
Birla Institute of Technology,
Mesra,Ranchi
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BIRLA INSTITUTE OF TECHNOLGY, MESRA, RANCHI

INDEX

SNO. TOPIC PAGE
1. COVER 1
2. INDEX 2
3. SCHEDULE 3
4. ACKNOWLEDGEMENT 4
5. NEW POWER HOUSE 5
5.1 INTRODUCTION 6
5.2 TRANSFORMER 7
5.3 CIRCUIT BREAKER 10
5.4 RMU PANEL 12
5.5 CABLES 15
6. TIKIAPARA CARSHED 17
6.1 INTRODUCTION 28
6.2 AIR CONDITIONING 19
6.3 END ON GENERATION 26
6.4 SELF GENERATION 30
6.5 TRAIN LIGHTING 35
7 BIBLIOGRAPHY 40
8. REMARKS 41







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SUMMER TRAINING 2014

The entire summer training in the D.E.E.(G) division was divided into three parts-
New Power House, Howrah

Air Conditioning Division, Coaching Complex, Tikiapara

Train Lighting Division, Coaching Complex, Tikiapara

















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ACKNOWLEDGEMENT

I would like to express my gratitude to Indian Railways for allowing me to pursue eighteen day training in
its General Electrical Department under the guidance of Divisional Electrical Engineer (G) / Howrah and
AEE(G)/HWH. I would also remain thankful to Additional Divisional Railway Manager, Howrah who
approved my training letter and his office for thorough support. I would express my gratitude to all Sr.
Engineer (Electrical) of NPH/HWH, ACC/TKPR and TL/TKPR for their support as well as their technical help
in getting the idea of various technical aspects in running of their departments. I would also thank all the
J.E.Es who helped me all along the training with their knowledge and experience and I am happy that I
have a fair idea of the work that goes around in all the departments mentioned above.
I would remain thankful to Prof. P.R.Thakura , training coordinator of Electrical and Electronics
Department, BIT Mesra, Ranchi for allowing me to pursue training in Eastern Railways (Indian Railways).


















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NEW POWER HOUSE,
HOWRAH










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1. INTRODUCTION

The NPH Howrah was established on 13
th
January 2012. This substation is governed by and
owned by Indian Railway. It is newly made sub-station which is being modified from old power
house, used to be known as New Transformer House. The substation is equipped with all the
latest versions of RMU panels with SF6 circuit breakers which is the latest technology
introduced in India.
The Calcutta Electric Supply Corporation (CESC) provides the NPH 3 phase, 6KV supply to this
6KV/11KV/415KV substation at Howrah. There are two Diesel Generators which is being used
in case of power failure. This power house fulfils the requirement of Eastern Railway, Howrah
Division. There are 5 transformers in total- three 1600 KVA , 6KV/11KV step-up and two
1000KVA ,11KV/415KV.



















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2. TRANSFORMERS
A transformer is an electrical device that transfers energy between two circuits through electromagnetic induction. A
transformer may be used as a safe and efficient voltage converter to change the AC voltage at its input to a higher or
lower voltage at its output without changing the frequency. Other uses include current conversion, isolation with or
without changing voltage and impedance conversion.
A transformer most commonly consists of two windings of wire that are wound around a common core to provide
tight electromagnetic coupling between the windings. The core material is often a laminated iron core. The coil that
receives the electrical input energy is referred to as the primary winding, the output coil is the secondary winding.
An alternating electric current flowing through the primary winding (coil) of a transformer generates a varying
electromagnetic field in its surroundings which induces a varying magnetic flux in the core of the transformer. The
varying electromagnetic field in the vicinity of the secondary winding induces an electromotive force in the secondary
winding, which appears as a voltage across the output terminals. If a load is connected across the secondary winding,
a current flows through the secondary winding drawing power from the primary winding and its power source.
There are generally two types of transformers-
1. Power Transformers.
2. Instrument Transformers.
2.1 WORKING PRINCIPLE:
The operation of a transformer is based on two principles of the laws of electromagnetic induction: An electric current
through a conductor, produces a magnetic field surrounding the conductor, and a changing magnetic field in the
vicinity of a conductor induces a voltage across the ends of that conductor.
The magnetic field excited in the primary coil gives rise to self-induction as well as mutual induction between coils.
This self-induction counters the excited field to such a degree that the resulting current through the primary winding
is very small when the secondary winding is not connected to a load.
The physical principles of the inductive behavior of the transformer are most readily understood and formalized when
making some assumptions to construct a simple model which is called the ideal transformer. This model differs
from real transformers by assuming that the transformer is perfectly constructed and by neglecting that electrical or
magnetic losses occur in the materials used to construct the device.
Ideal transformer


Ideal transformer with a source and a load.N
P
and N
S
are the number of turns in the primary and secondary windings
respectively.
The assumptions to characterize the ideal transformer are:
Transformer's windings have no resistance. Thus, there is no winding copper loss, and hence no voltage drop.
Flux is confined within the magnetic core. Therefore, the same flux links input and output windings.
Transformer core's magnetic permeability is infinitely high, implying zero net m.m.f. (amp-turns) (otherwise there
would be infinite flux), and hence I
P
N
P
- I
S
N
S
= 0.
Transformer core does not manifest magnetic hysteresis or eddy currents, which cause inductive loss.
If the secondary winding of an ideal transformer has no load, no current flows in the primary winding.
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The circuit diagram (right) shows the conventions used for an ideal, i.e. lossless and perfectly coupled transformer
having primary and secondary windings with N
P
and N
S
turns, respectively.
The ideal transformer induces secondary voltage V
S
as a proportion of the primary voltage V
P
and respective winding
turns as given by the equation
VP/VS=NP/NS=a
Where a is the winding turns ratio, the value of these ratios being respectively higher and lower than unity for step-
down and step-up transformer, designates source impressed voltage,V
S
designates output voltage.
According to this formalism, when the number of turns in the primary coil is greater than the number of turns in the
secondary coil, the secondary voltage is smaller than the primary voltage. On the other hand, when the number of
turns in the primary coil is less than the number of turns in the secondary, the secondary voltage is greater than the
primary voltage.
Any load impedance Z
L
connected to the ideal transformer's secondary winding allows energy to flow without loss
from primary to secondary circuits. The resulting input and output apparent power are equal as given by the equation
IP*VP=IS*VS



2.2 POWER TRANSFORMER:Generation of electrical power in low voltage level is very much cost effective.
Hence electrical power is generated in low voltage level. Theoretically, this low voltage level power can be
transmitted to the receiving end. But if the voltage level of a power is increased, the electric current of the power is
reduced which causes reduction in ohmic or I2R losses in the system, reduction in cross sectional area of the
conductor i.e. reduction in capital cost of the system and it also improves the voltage regulation of the system.
Because of these, low level power must be stepped up for efficient electrical power transmission. This is done by step
up transformer at the sending side of the power system network. As this high voltage power may not be distributed
to the consumers directly, this must be stepped down to the desired level at the receiving end with the help of step
down transformer. These are the uses of electrical power transformer in the electrical power system.

2.3INSTRUMENT TRANSFORMER:Instrument transformers means current transformer & voltage transformer
are used in electrical power system for stepping down currents and voltages of the system for metering and
protection purpose. Actually relays and meters used for protection and metering, are not designed for high currents
and voltages. High currents or voltages of electrical power system can not be directly fed to relays and meters. CT
steps down rated system current to 1 Amp or 5 Amp similarly voltage transformer steps down system voltages to 110
V. The relays and meters are generally designed for 1 Amp, 5 Amp and 110 V.
2.3.1.CURRENT TRANSFORMER:A CT functions with the same basic working principle of electrical power
transformer, as we discussed earlier, but here is some difference. If a electrical power transformer or other general
purpose transformer, primary current varies with load or secondary current. In case of CT, primary current is the
system current and this primary current or system current transforms to the CT secondary, hence secondary current
or burden current depends upon primary current of the current transformer.In a power transformer, if load is
disconnected, there will be only magnetizing current flows in the primary. The primary of the power transformer takes
current from the source proportional to the load connected with secondary . But in case of CT, the primary is
connected in series with power line. So current through its primary is nothing but the current flows through that
power line. The primary current of the CT, hence does not depend upon whether the load or burden is connected to
the secondary or not or what is the impedance value of burden. Generally CT has very few turns in primary where
secondary turns are large in number.
2.3.2POTENTIAL TRANSFORMER:Potential transformer or voltage transformer gets used in electrical power
system for stepping down the system voltage to a safe value which can be fed to low ratings meters and relays.
Commercially available relays and meters used for protection and metering, are designed for low voltage.A voltage
transformer theory or potential transformer theory is just like a theory of general purpose step down transformer.
Primary of this transformer is connected across the phase and ground. Just like the transformer used for stepping
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down purpose, potential transformer i.e. PT has lower turns winding at its secondary. The system voltage is applied
across the terminals of primary winding of that transformer, and then proportionate secondary voltage appears
across the secondary terminals of the PT.The secondary voltage of the PT is generally 110 V.
2.2 RATINGS OF TRANSFORMERS IN NEW POWER HOUSE
6KV/11KV TRANSFORMER: 11KV/415V TRANSFORMER:
KVA: 1600 1000
HV: 11000V (RAILWAY SIDE) 11000V (RAILWAY SIDE)
LV: 6000V (CESC) 415V (SUPPLY TO OLD ,NEW COMPLEX)
AMPS- HV: 52.5A52.5A
LV: 96A 1391.2A
PHASE: 3 3
TYPE OF COOLING:
OIL NATURAL AIR NATURAL (ONAN) OIL NATURAL AIR NATURAL (ONAN)
FREQUNECY: 50 Hz 50 Hz
WEIGHT OF OIL: 400 KGS. 770 KGS.
SAFETY TEMP:50 C50 C
VECTOR GROUP: Yd11 Dyn11
TAPPING: PRESENT PRESENT
INTERNAL RESISTANCE VALUES:
HT TO EARTH: 11700 MEGOHMS.
LT TO EARTH: 9950 MEGOHMS.
HT TO LT: 15200 MEGOHMS.
BDV OF OIL: 67.4 KV

2.3 SAFETY DEVICES IN TRANSFORMER
2.3.1 TRANSFORMER OIL:The oil helps cool the transformer. Because it also provides part of the electrical
insulation between internal live parts, transformer oil must remain stable at high temperatures for an extended
period. To improve cooling of large power transformers, the oil-filled tank may have external radiators through which
the oil circulates by natural convection. Very large or high-power transformers (with capacities of thousands of kVA)
may also have cooling fans, oil pumps, and even oil-to-water heat exchangers.
Large, high voltage transformers undergo prolonged drying processes, using electrical self-heating, the application of a
vacuum, or both to ensure that the transformer is completely free of water vapor before the cooling oil is introduced.
This helps prevent corona formation and subsequent electrical breakdown under load.
2.3.2 BUCHHOLZ RELAY:A Buchholz relay is a safety device mounted on some oil-filled power transformers and
reactors, equipped with an external overhead oil reservoir called a conservator. The Buchholz Relay is used as a
protective device sensitive to the effects of dielectric failure inside the equipment.
Depending on the model, the relay has multiple methods to detect a failing transformer. On a slow accumulation of
gas, due perhaps to slight overload, gas produced by decomposition of insulating oil accumulates in the top of the
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relay and forces the oil level down. A float switch in the relay is used to initiate an alarm signal. Depending on design,
a second float may also serve to detect slow oil leaks.

If an arc forms, gas accumulation is rapid, and oil flows rapidly into the conservator. This flow of oil operates a switch
attached to a vane located in the path of the moving oil. This switch normally will operate a circuit breaker to isolate
the apparatus before the fault causes additional damage. Buchholz relays have a test port to allow the accumulated
gas to be withdrawn for testing. Flammable gas found in the relay indicates some internal fault such as overheating or
arcing, whereas air found in the relay may only indicate low oil level or a leak.
2.3.3 EXPLOSION VENT:An explosion vent or rupture panel is a safety device to protect equipment or
buildings against excessive internal, explosion-incurred pressures, by means of pressure relief. An explosion vent will
relieve pressure from the instant its opening (or activation) pressure has been exceeded.

3. CIRCUIT BREAKERS
Electrical circuit breaker is a switching device which can be operated manually as well as automatically for controlling
and protection of electrical power system respectively. As the modern power system deals with huge currents, the
special attention should be given during designing of circuit breaker to safe interruption of arc produced during the
operation of circuit breaker.
The circuit breaker mainly consists of fixed contacts and moving contacts. In normal "on" condition of circuit breaker,
these two contacts are physically connected to each other due to applied mechanical pressure on the moving
contacts. There is an arrangement stored potential energy in the operating mechanism of circuit breaker which is
realized if switching signal given to the breaker. The potential energy can be stored in the circuit breaker by different
ways like by deforming metal spring, by compressed air, or by hydraulic pressure. But whatever the source of
potential energy, it must be released during operation. Release of potential energy makes sliding of the moving
contact at extremely fast manner. All circuit breaker have operating coils (tripping coils and close coil), whenever
these coils are energized by switching pulse plunger inside them displaced. This operating coil plunger is typically
attached to the operating mechanism of circuit breaker, as a result the mechanically stored potential energy in the
breaker mechanism is released in forms of kinetic energy, which makes the moving contact to move as these moving
contacts mechanically attached through a gear lever arrangement with the operating mechanism. After a cycle of
operation of circuit breaker the total stored energy is released and hence the potential energy again stored in the
operating mechanism of circuit breaker by means of spring charging motor or air compressor or by any other means.
There are 4 types of circuit breakers :
3.1AIR CIRCUIT BREAKERS:The working principle of this breaker is rather different from those in any other
types of circuit breakers. The main aim of all kind of circuit breaker is to prevent the reestablishment of arcing after
current zero by creating a situation where in the contact gap will withstand the system recovery voltage. The air
circuit breaker does the same but in different manner. For interrupting arc it creates an arc voltage in excess of the
supply voltage. Arc voltage is defined as the minimum voltage required maintaining the arc. This circuit breaker
increases the arc voltage by mainly three different ways. It may increase the arc voltage by cooling the arc plasma. As
the temperature of arc plasma is decreased, the mobility of the particle in arc plasma is reduced, hence more voltage
gradient is required to maintain the arc.It may increase the arc voltage by lengthening the arc path. As the length of
arc path is increased, the resistance of the path is increased, and hence to maintain the same arc current more
voltage is required to be applied across the arc path. That means arc voltage is increased. Splitting up the arc into a
number of series arcs also increases the arc voltage.
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3.2 OIL CIRCUIT BREAKERS:The operation of oil circuit breaker is quite simple lets have a discussion. When the
current carrying contacts in the oil are separated an arc is established in between the separated contacts.
Actually, when separation of contacts has just started, distance between the current contacts is small as a result the
voltage gradient between contacts becomes high. This high voltage gradient between the contacts ionized the oil and
consequently initiates arcing between the contacts. This arc will produce a large amount of heat in surrounding oil
and vaporizes the oil and decomposes the oil in mostly hydrogen and a small amount of methane, ethylene and
acetylene. The hydrogen gas cannot remain in molecular form and it is broken into its atomic form releasing lot of
heat. The arc temperature may reach up to 5000oK. Due to this high temperature the gas is liberated surround the arc
very rapidly and forms an excessively fast growing gas bubble around the arc. It is found that the mixture of gases
occupies a volume about one thousand times that of the oil decomposed. From this figure we can assume how fast
the gas bubble around the arc will grow in size. If this growing gas bubble around the arc is compressed by any means
then rate of de ionization process of ionized gaseous media in between the contacts will accelerate which rapidly
increase the dielectric strength between the contacts and consequently the arc will be quenched at zero crossing of
the current cycle.


3.3 SF6 CIRCUIT BREKAERS:A circuit breaker in which the current carrying contacts operate in sulphur
hexafluoride or SF6 gas is known as an SF6 circuit breaker.SF6 has excellent insulating property. SF6 has high electro-
negativity. That means it has high affinity of absorbing free electron. Whenever a free electron collides with the SF6
gas molecule, it is absorbed by that gas molecule and forms a negative ion.The attachment of electron with SF6 gas
molecules may occur in two different ways,
1) SF6 + e = SF6 -
2) SF6 + e = SF5 - + F
These negative ions obviously much heavier than a free electron and therefore over all mobility of the charged
particle in the SF6 gas is much less as compared other common gases. We know that mobility of charged particle is
majorly responsible for conducting current through a gas.
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3.4 VACUUM CIRCUIT BREAKERS:A vacuum circuit breaker is such kind of circuit breaker where the arc
quenching takes place in vacuum. The technology is suitable for mainly medium voltage application. For higher
voltage vacuum technology has been developed but not commercially viable. The operation of opening and closing of
current carrying contacts and associated arc interruption take place in a vacuum chamber in the breaker which is
called vacuum interrupter. The vacuum interrupter consists of a steel arc chamber in the centre symmetrically
arranged ceramic insulators. The vacuum pressure inside a vacuum interrupter is normally maintained at 10 - 6 bar.

4. RMU PANEL
A standard piece of switchgear in distribution systems comprising of switches for switching power cable rings and of
switches in series with fuses for the protection of distribution transformers is called RMU or Ring Main Unit. RMU
used for H.T.side. RMU is having 3no.s of switches (Circuit Breakers or Isolators or LBS), it is used for two inputs with
mechanical or electrical interlock and one outgoing to the load. Either one input with two outgoings. RMU is used for
redundancy feeder's purpose.
Ring main unit is used in a secondary distribution system. It is basically used for an uninterrupted power supply.
Alongside, it also protects your secondary side transformer from the occasional transient currents. Depending on your
applications and loading conditions you can use a switch fuse combination or a circuit breaker to protect the
transformer. This transformer connected to the switch fuse/ circuit breaker is called your T off. In a common
arrangement you have Load break switch on both the sides of your T off. Ring main Units come in standard ratings of
11/22/33 kV, 630/1250 A, 21 KA/3 seconds.

4.0 HV Switchgear:Multi-panel switchboards or ring main units (RMUs) control 6kV and 11kV networks. Both
networks are connected as ring circuits butoperate as radial feeds. Each ring has a third feeder coupled,
wherepossible, at a node representing one half of the total ring current. Thedistribution feeders are protected against
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over-current and earth faults at themain switchboards and do not rely on intermediate downstream
protection.Therefore, incoming circuits on intermediate switchgear panels are notequipped with protection relays
and are used for manual sectionalising only.This replicates the function of the ring switches on RMUs.Multi-panel
switchboards are used in substations where a third feederinterconnection is made and/or other switched HV
functions are requirede.g. PFC Capacitors and remotely switched transformer feeders.RMUs are used in substations
utilizing plain transformer feeders and offercost and possible space savings over multi-panel switchboards.
Furthersavings are made if the RMUs can be close coupled to the transformers and some substations are equipped
with up to 3x1600kVA transformers connected in this way.

4.1 HV Multi-panel Switchboards: Manufacturers and incorporate the following:
12kV minimum rms working voltage
630A minimum circuit breaker and bus-bar rating
25kA 3s symmetrical fault rating
MicomP125 protection device on transformer feeders only. Device equipped with auxiliary relays to receive LV
intertrip and lockout signals.
Vacuum breaking medium
Bus-section circuit breaker
All circuit breakers to be independent manual closing control and fitted with 30V DC trip coil for local manual and
protection trips
All circuit breakers to have lockable electrical trip control switches
One set of auxiliary contacts shall be wired out on the transformer panels to provide an inter-trip signal to the
transformer LV circuit breaker, which also acts as an interlock to prevent closure of the LV circuit breaker until the HV
circuit breaker is closed.

4.2 HV Ring Main Units (RMUs):Manufacturers and incorporate the following:
Through symmetrical fault rating 25kA 3s
Independent manual ring switch operation with minimum 630A rating for load switching and through fault making
capacity.
200A rated vacuum or SF6 circuit breaker for controlling outgoing transformer feeder.
Circuit breaker symmetrical breaking capacity of 21kA 1s
Non-TLF protection e.g. Schneider VIP 300 unit or discrete relay as in 1.1
30V DC shunt trip coil
One set of auxiliary contacts shall be wired out on the transformer panels to provide an inter-trip signal to the
transformer LV circuit breaker, which also acts as an interlock to prevent closure of the LV circuit breaker until the HV
circuit breaker is closed
Suitable for close coupling to the transformer. Close coupled RMUs to have ground braced framework and not rely
on the transformer LV flange for sole support.
4.3 PARTS OF AN RMU PANEL:
1. Fuse room
2. Capacitive voltage indicators
3. Short-circuit ground fault indicator
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4. Pressure indicator
5. Serial no. of signs
6. Analog circuit diagrams
7. Fuse indicator
8. Panel padlock device
9. Cable compartment
10.IDS installation room
11.RONIS lock
12 Circuit breakers( SF6)
13. Load switch operation hole
14. Ground swith operation hole
15. Operating switch
16. Closing switch
4.3.1 SWITCHING DEVICES:
LOAD BREAK SWITCH:they have to be designed according to IEC 60265 standards. The direction of rotation must
be clockwise for ON position and counterclockwise when switching OFF the load break switch.
EARTHING SWITCH: each switching device should be equipped with an inbuilt integrated switch. The earthing must be
according to IEC 60129 standards. The earthing switch with making capacity must be integrated in a comprehensive
integrator interlocking system and must be equipped with an ON snap action drive.
1. CABLE FEEDER
The ring main unit must be equipped with the outer cone connection bushings M16 inside thread. The cable
connection compartment of the cable switches or isolators must be dimensioned in such a way that surge arrestors
and parallel cables can be installed behind the front covers.
The connecting points of each outgoing feeder must be horizontally situated in one level at a suitable height from the
bottom line of the unit for easy connection.
2. TRANSFORMER FEEDER
The transformer feeder must be equipped with outer cone bushings for bolted cable connection systems. The cable
connections at the transformer feeder must be accessible from the front. Lateral or rear situated connections will not
be accepted. It must be possible to connect the transformer cables by means of straight or angled plugs depending on
the available space without exceeding the outer dimensions of RMU.
3. INTERROGATOR INTERLOCKING SYSTEM
The switchgear must be equipped with a comprehensive interlocking system, which prevents inadmissible control
process and does not allow any wrong operation. The following interlocks must be present-
load break switch, earthing switch- cable front cover, earthing switch for circuit breaker covers.
4. ACTUATING UNITS
The plug in holes/access for hand crank or drive sockets, for load break switches and those for earthing devices should
be distinctive and should be mechanically connected to the respective position indicator. The operating handles for
load break devices and earthing devices must be distinctive and have different colour.
4.3.2 SECONDARY EQUIPMENTS:
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1. VOLTAGE DETECTING SYSTEM
Every cable feeder and transformer feeder must be equipped with a 3-phase integrated voltage detection system. The
energy for the system should be from the coils present at the outer cone of connection bushings.
2. FAULT PASSAGE INDICATOR
As an option it must be possible to fit cable feeders with fault passage indicators that can be easily watched on the
front panel.
The transducers for the short circuit indicators have to be mounted onto the outer connection bushings or on the
incoming cables to the RMU. The display of FPI should be by LCD/LED.

3. MOTOR DRIVE
It should be possible to change the manual drives of the load break switches to motorized drives at site. The motor
drives have to be integrated into the recess of the drives. All the mechanical interlocking must also work when the
load break switches are operated by motor drive. In the case of power failure of the auxiliary circuit the manual
operation of the operation devices must be possible by means of operating handle.
4.3.3 RELAY:
The relay should be self-powered/ CT type. Preferably, combination of a contact protection relay and related ring type
transformer should provide the protection. The relay should provide time over current protection and earth fault
protection functions in a well proven technique for CT powered protection relays.
The following functions should be realized:-
1. 3 phase definite time overcurrent and short circuit protection with variable tripping times.
2. 3 phase overcurrent protection with selectable inverse time characteristics and definite time short circuit
element.
3. Earth current protection.

5 . CABLES
5.1 PILC CABLES:PILC cables are used in power distribution and industrial applications, and they may be installed
exposed, in underground ducts or directly buried. Their design begins with annealed, bare copper conductor(s) which
may be round, concentric, compressed or compact stranded, compact sector, and in larger sizes Type M segmental
stranded. An example of compact sector conductors is shown in the illustration. The insulated cable core is
impregnated with a medium viscosity polybutene-based compound. The combination of the excellent electrical and
mechanical characteristics of the liquid and the paper has resulted in a reliable and economic insulation, which now
claims a history of almost 100 years. It is little wonder why so many utilities and power-consuming industries, still
continue to specify PILC. To prevent the ingress of moisture, a seamless lead-alloy sheath is applied. The outer jacket
may be PVC or PE, and if required by the application, armour is available.


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5.2XLPE CABLES: Cross linked polyethylene insulated power cable (XLPE cable), having no necessity of metallic
sheath, has much flexibility and is light in weight as compared with the conventional paper insulated cable. Nowadays
XLPE cable is widely applied from 600 V to 154 kV transmission lines. Owing to the excellent electrical characteristics,
XLPE cable has an advantage of greater continuous and short-circuit current carrying capacity. In addition to that, it is
easy in handling and installing as compared with the conventional paper insulated and lead sheathed cables.
Furthermore, it is trouble-free in maintenance and simple in terminating and jointing. XLPE cable is now applied for up
to 275 kV lines in place of PILC cable and now 500 kV line XLPE cable has been studied for practical application in the
near future.


















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TIKIAPARA COACHING
DEPOT,
TIKIAPARA, HOWRAH









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INTRODUCTION

Tikiapara Coaching Depot maintains 22 primary base trains and 6 round trip trains. Total coach
holding capacity is 744 coaches. It handles prestigious trains like Rajdhani Express and Duronto
Express. The Coaching Depot is under Howrah Division, Eastern Railway. Coaching
maintenance shed at Tikiapara is one of the biggest coach maintenance depot of IR holding
fluctuates between 1700 to 2000 coaches.
















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1. AIR CONDITIONING
Air conditioning which deals with the comforts of human beings in an enclosed conditioned space is known as
Comfort Air Conditioning. There are a number of factors that influence the comfort conditions.Comfort air
conditioning has been defined by Dr. D.W. Carrier as under:
Artificial simultaneous control within enclosures of variable humidity, temperature, air motion and air cleanliness.
Odour control is another factor concerning comfort which has been subsequently included in the above definition.
Any change in these conditions results in a change in the physiological functions of the body and the body tries to
adjust itself to the changing outside conditions. The performance of adjustments takes time and sensation of comfort
or discomfort would depend upon the quick or slow adjustment. Often the adjustment may not be reached with
consequent increase in discomfort.

1.1 AIRCONDITIONING OF RAILWAY COACHES
Passengers in a railway travel are adversely affected by infiltration of air unpleasantly laden with dust due to open
windows. This is more so in case of high speed passenger carrying trains. Secondly for a tropical country like India, the
temperature varies from 46 degree C during summer to 2 degree C during winter. Air conditioning of railway coaches
is, therefore, necessary for the maximum comfort and well-being of passengers in a railway travel. In keeping with
modern trend, air conditioning of coaches for upper class travellers and lately even for lower class travellers have
been introduced by the Indian Railways.

REQUIREMENTS OF RAILWAY COACH AIRCONDITIONING SYSTEM
Supplying clean fresh air at a controlled uniform temperature.
Catering, within the confines of the Railway carriages to the continuously changing number of passengers.
Providing for heating as well as cooling on a train that travels through areas of widely differing climate during its
journey.
Operation of the equipment from power generated, stored and controlled on the train
CLASSIFICATION OF AIR CONDITIONED COACHES


SELF GENERATED END ON GENERATED


BG MG

AC-2T
3AC 2AC ACC COMPO ECC

AC3T AC2T AC-1 ACC DRIVING PANTRY POWER
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1.2 SELF GENERATED COACHES:
The electrical power for the self-generating type of coaches is derived from the alternator mounted on bogie transom
of the coach and driven by the axle through 'V belt drive as long as the coach is in motion at the minimum full load
output (MFO) speed of the alternator. During stationary or when the coach is running at less than MFO speed the
entire coach load is met by the battery of 800 AH capacity. Provision for charging and precooling the coach from
external supply has been made by means of battery charger, 200A rating mounted on the coach under frame. Two
numbers of 415 V, 3 phase, ac, pre cooling sockets have been provided diagonally on the end walls. The alternator
working in association with rectifier cum regulator gives an output of 18 KW at 130 V, DC in the underslung type of AC
coach, whereas the alternator capacity is 25Kw in the RMPU AC coach. One alternator set per AC plant has been fitted
in the self-generating type AC coaches. Power supply demand for AC equipments is met from axle driven transom-
mounted brushless alternator which is rated for 110 V DC supply. At low speeds and during halts the power
requirement is met from 110 V lead acid battery housed in battery boxes mounted on the underframe of the coach.
1.3 END-ON GENERATED COACHES:
The electrical power supply for end on generation type AC coaches is derived from separate generator cars marshalled
at the ends of the train formation, with generation and transmission voltage of 415 V, 3 ph, AC. The power for
individual coaches is tapped by means of rotary switch from any one of the double feeders running along the coach
leading from the power cars, and coupled between coaches by means of inter-vehicular couplers. The air conditioning
equipment works at 415V, 3 phase AC supply and train lighting equipment work at 110V, AC, obtained between phase
and neutral derived from a 3 KVA,415/190V, 4 wire step down transformer. AC coaches draw power from the diesel-
generating sets carried in coaches put in the front and rear of the rake, functioning at 415/750 V, 3 phase, 50 Hz AC
supply. The power is distributed to entire rake and thus to each coach through two sets of 3 phase 415/750 V feeders.
Each coach is provided with control, distribution and feeder changeover arrangement on 415/750 V control panel. The
AC equipments operate at 415 V, 3 phase, 50 Hz AC supply.
The airconditioning system in both types (SG or EOG) of Indian Railways stipulates use of open type compressor,
condenser,liquid receiver with dehydrator separately mounted on the underframe of the coach. The evaporator
comprising cooling coils, heater elements and blower fans with motor is mounted between coach roof and false
ceiling. The conditioned air is blown through the central duct and distributed inside the coach through adjustable grills
diffusers.
1.4 DRIVING EQUIPMENTS:
Driving equipments consist of motors for driving the compressor, condenser impeller fans and the evaporator blower
fans. The driving motors in self generating type coaches are all of D.C. machines needing more care for attention of
commutator and brushes. The E.O.G. type coaches are provided with 3 phase AC squirrel cage induction motors for
driving the AC equipments.













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1.6 A/C EQUIPMENT IN RAILWAY COACHES:
This consists of the following:
Evaporator Unit.
Compressor.
Condenser Unit.
Gauge panel.
A/C control panel.
Air Duct.
Refrigerant piping & joints.
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Wiring.
1.6.1 Evaporator Unit
The evaporator unit consists of a thermostatic expansion valve, a heat exchanger, a resistance heating unit and
centrifugal blower driven by a motor The thermostatic expansion valve controls quantity of high pressure liquid
refrigerant and allow to expand to a lower pressure corresponding to the load demand The expanded refrigerant
passes through the distributor into the heat exchanger consisting of finned copper tubes. The return air from the air
conditioned compartment (75 %) is mixed with fresh air (25%) and this mixture is drawn/blown through the heat
exchanger, where heat in the air is transferred to the cool refrigerant causing cooling of the air and the evaporation of
the refrigerant inside the tubes. The cooled air is led through the ducting to the various compartments and diffused by
means of air diffusers Filters are provided in the fresh air and return air path to eliminate dust. When the outside
ambient temperature is very low, heater is switched on according to the setting of the thermostats.
1.6.2 Compressor
The refrigerant vapour drawn from the evaporator is compressed by means of a multi cylinder reciprocating
compressor and compressed to a pressure ranging from 10 to 15 Kg/Cm2 according to the load demand. The work
done due to compressor raises the temperature of the refrigerant vapour.
1.6.3 Condenser
The condenser serves the function of extracting the heat absorbed by the refrigerant vapour in the evaporator and
the heat absorbed during the compression process. The condenser consists of a heat exchanger, which is forced-air-
cooled by means of two or three axial flow impeller fans. The refrigerant vapour is liquified when ambient cool air is
passed through the heat exchanger. The refrigerant liquid leaving the condenser is led into the liquid receiver from
where it proceeds to the expansion valve on the evaporator. The liquid receiver is a cylindrical container which
contains a reserve of the refrigerant liquid. A dehydrator and filter are also provided to ensure that the refrigerant is
free from moisture and dust particles.
1.6.4 A/C control panel:
The control of the air conditioning system is achieved by means of air conditioning control panel. The design of the
various elements in the control panel takes into account the system safety requirements. The safety requirements for
the operation of the A/C system are listed as under:
a. The working of blower fan of the evaporator and the blower fan of the condenser have to be ensured before the
compressor starts functioning.
b. Suitable protection to ensure adequate lubrication of compressor to avoid piston seizure.
c. The excessive pressure on the discharge side of the compressor (High Head Pressure) should be avoided.
d. The suction pressure should not be lower than 0.7 Kg/Cm2 to prevent frosting of the evaporator.
e. The compressor motor has to be soft started to limit the sudden in rush of starting current.
f A suitable interlock has to be provided to ensure that heater is not on, when the compressor is working.
g A low voltage protection for compressor motor to ensure that voltage does not go below 100 volts in order to avoid
undue drain on battery.
h. The blower fan has to come 'ON before the heater comes 'ON'. Over load protection and short circuit protection
for all electrical circuits. The A/C control panel incorporates all the above safety requirements.






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1.6.5 Gauge panel
Gauge panel consists of pressure gauges (HP, LP, and OP) and pressure cutouts to protect the compressor against, (i)
High pressure, (ii) Low pressure and (in) low oil pressure.
1.6.6 High pressure cutout
It is a safety device against build up of excessive delivery pressures and protects the compressor and piping system
from damage. It is a pressure operated switch which switches off the compressor drive motor when the pressure
exceeds a preset value ( 17.6 Kg/Cm2). The plant can not be restarted unless the cutout is reset manually.
1.6.7 Low pressure cutout
It is also a pressure operated switch similar to the H.P. cutout switch, but it shuts down the compressor if the suction
pressure drops down below 0.7 Kg/Cm2. It protects the system against unduly low evaporator temperatures and
formation of frost on the evaporator. No manual reset is provided on this and therefore the compressor starts
automatically if the suction pressure rises above the preset.
1.6.8 Low oil pressure cutout
It ensures adequate lubrication of compressor to avoid piston seizure due to less lubricating oil or failure of oil pump.
This cutout is set at 2.5 Kg/Cm2.
1.6.9 Wiring
All wiring has been done by means of multi-stranded PVC insulated copper cables to specification. ICF/Elect./857. All
cables have been laid on steel trough/conduits for easy maintenance and prevent fire hazards. Crimped types of
connections have been adopted throughout. All the terminal boards are of fire retardant FRP material, Reliability of
wiring has been made very high.
1.7 Refrigerant Compressor
Hermetic or semi-hermetic refrigerant compressors working with Freon 22 (monochlorodifluoro methane) are
provided in the A/C package unit. The compressor motor is rated for 415V, 3Ph, 50 HZ, AC Power Supply.
Make & Model Kirloskar. Hermetically Sealed.
Power Consumption 5. 25KW +/-20% depending upon Ambient temp.
Current (Amps.) 8.25 +/- 25% at 415V, 3Ph,50HZ,AC Power Factor - 0.8
C.F.M. 12.033
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Volume 117.65 CC/Rev. Refrigerant Condenser
1.8 Refrigerant Condenser
Condenser Coil Fin-on-Tube
Face Area O.67 M2 x 2
Material of tube Copper
Refrigerant R22,Less than 3.0Kg each circuit
Condenser Fan Propeller type (2 Nos)
Diameter 533.4 mm (21 x 2)
Air Flow (CFM) 5000 min. x 2
Pressure (External Static) Open to atmosphere
Speed (RPM) 1400 +/- 10%
Motor size 1 H.P x 2
Current consumption (Amps) 1.8 +/- 10%x2 at 415V, 3 Ph, 50 HZ, AC
Power Factor 0.7

1.9 Evaporator Unit Fin-on-tube type
Evaporator Fan Centrifugal type blower
Diameter 254-279 mm (10-11 )
Air Flow (CFM) 2000 (3400 cu Mtr/Hr.)
Pressure (External Static) 20 mm. Min. water gauge
Speed (RPM) Motor size 1400 +/- 10%
Speed (RPM) Motor size 1.5 Hp
Current consumption(A) 2.2 +/- 10% at 415V, 3ph, 50HZ, AC
Power Factor 0.7
1.10 POWER SUPPLY ARRANGEMENT
The electrical load in the coach is fed through two sets of 415V, 3Ph, AC, 4 wire feeders run along the rake and
coupled to the coach with the help of inter vehicular couplers. Each coach on the rake is provided with the control,
distribution and feeder changeover arrangement on 415V control panel. The 415V, 3Ph, supply is transformed with
the help of a 415/190V, delta/star, 3Ph, transformer of 3KVA capacity for supplying the light and fan loads. A separate
control panel/junction box is provided inside the coach for control and distribution of 3Ph, 4 wire, 190V (110V, 1Ph)
system for lights and fans. Two sets of latched and electrically interlocked coupling of cable and plug socket and
dummy socket one at each end panel of the coach is provided for transmitting the feed to the adjacent coaches on
either side. Water raising apparatus is fed at 240V, 1Ph, 50 HZ, AC. One emergency lighting battery 24V, 90AH is
provided on the under frame to feed emergency lights in case of failure of power supply. One battery charging
transformer rectifier unit is provided on the under frame to charge emergency lighting battery.




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2. END ON GENERATION
With the increase in demand for faster trains having limited halts and improved passengers amenities - air
conditioning, fluorescent lighting, catering from pantry cars, Rajdhani/ Shatabdi Express services have been
introduced on many routes. Rajdhani Express trains, were initially introduced on NDLS - Howrah, New Delhi-Bombay
Central routes. These trains operate at 130-140 kmph. To reduce the resultant noise and dust problems, all the
coaches including the service coaches like pantry-car of the trains occupied by operating personnel like Guard and the
crew in the power car ore sealed and hence air-conditioned. Since the power required for operating air-conditioning
load., cooking ranges/ refrigerators/ bottle coolers in pantry cars is considerable, use of power cars equipped with
Diesel generating sets is the only way, at present.
To reduce with number of power cars from 3 to 2 and to feed the entire load of train from either of power cars, the
capacity of DG sets has been increased from 125 KW to 250 KW and generation voltage has also been increased from
415 V to 750 V with a view to overcoming the of voltage drop in feeding system. 750 V power cars are the first and
last vehicle in the EOG rake. Schematic diagram of the EOG system is at Fig. 8-1. Two feeders run all along the entire
rake through I.V. couplers. Each coach on the rake is provided with the control, distribution and feeder changeover
arrangements in the 750/ 415 V control panel. 750 V, 3 phase supply is stepped down to 415 V, 3 phase, 50 cycles by a
step down transformer to feed the A.C. equipments. To make coach suitable for 415V supply system, contactors with
interlocks are provided to bypass the step down transformer. The 415 V, 3 phase supply is stepped down through
415V/ 190V, Delta Star transformer. A separate panel is provided for control and distribution of 3 phase 4 wire, 190
volts for working lights and fans at 110 V, single phase. Emergency lights provided in the power cars comes 'ON'
automatically through No-Volt contactor which energizes lamps from batteries as soon as main power supply
interrupts for any reason.
2.1 CAPACITY OF BRUSHLESS ALTERNATORS AND OF DIESEL ENGINE:
Load on both the feeders 560 KW
Load on each feeder - 280/0.8 KVA
Required output of Alternator ~ 350 KVA
500 KVA capacity alternators are being used to cater the future increase in load, derating
factor, unbalance in the load etc.
Two type of Diesel Engines are being used for high capacity 750 V Power cars:
Kirloskar Cummins. KTA - 1150 G 450 BHP at 38 degree C
(427 BHP at 55 degree C)
INTACH 3406 B 398 BHP at 55 degree C
Kirloskar Cummins Engines are coupled with brushless Alternator of KEC make (Kirloskar Electric Company Bangalore).
INTACH 3406 B engines are coupled with Brushless Alternators of KEL (Kerala Electrical) make.

2.1.1 Principle of working of Brushless Alternator:
Unlike brushless Alternators used in self generating coaches, which have no windings on rotor and are less efficient,
Brushless Alternators used on BOG system have windings both on stator as well as rotor. Brush gear is eliminated with
provision of rotating diodes in the excitation system. Three phase output is collected from stator of main Alternator
(G) & field is wired on rotor. Three phase output from stator is also rectified and through a regulator (Rg) fed to the
stator of Exciter (E) which is mounted on main shaft. Three phase Output from rotor to Exciter (E), is rectified through
rotating diodes and fed to the rotor of main Alternator (G). The need for brushes, is therefore eliminated.


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2.1.2 PROTECTIVE DEVICES:
a) Diesel Engine Protection
Following protective devices are provided for Diesel Engine :
i) High water temperature
ii) Low water level in radiator
iii) Low lubricating oil
iv) Over speed
The high water temperature protective device cuts off the load automatically and the engine returns to idling speed
and the other devices cut-off the load as well as shut-down the engine. All the protective devices are designed to give
audio-visual indication when they operate.
b) ALTERNATOR PROTECTION
Alternators are provided with following protective devices :
a) Alternator overload.
b) Under voltage.
c) Earth leakage.
d) Short circuit
c) FEEDER PROTECTION
Following devices are provided for feeder protection
i) Feeder Earth leakage.
ii) Feeder overload.

















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SCHEMATIC OF POWER SUPPLY IN COACHES


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3. SELF GENERATION SYSTEM
3.1 INTRODUCTION:Coaches provided with D.C. dynamo/brushless alternator were driven from coach axle
through flat belt or V belts on pulleys. The pulleys are mounted on axle as well as dynamo/brushless alternator. The
generation equipment used for axle generation is as follows
a) 60 A and 100 A Dynamos with inherent regulation
b) 100 A (3 KW) and 150 A (4.5 KW) brushless alternators with external regulation for MG & BG respectively.
All D.C dynamos have already been replaced by brushless alternators in view of simplicity in maintenance and
superior characteristics for both high and low speed. No new DC dynamos are being procured and this system is
practically non-existent at present. Lead acid batteries of standard capacity 210 Ah, or 320 Ah are provided in each
coach depending on the connected load of the coach. Normally, each coach should be able to meet its own load
independently. Emergency feed terminal boards are provided at each end of the coach to enable feeding from the
adjoining coaches on either side. This emergency feed is availed of only in case the coach is unable to feed the load
due to missing/defective generating equipment, regulator or batteries.
3.2 AXLE GENERATION:This system has proved more reliable and capable of meeting future increase in load. It
has, therefore, been adopted as standard for all future builds of self-generating, coaches. In this system 4.5 KW
brushless alternators are driven through V-belts from axle. Lead acid batteries 11O V, 120 Ah arranged from 3 cell
Mono-block units, are provided in the B.G. coaches. Four numbers of emergency feed terminals boxes for B.G. and
one number for M.G. coach, are provided on each end wall for interconnecting the coach to adjacent coach to receive
power, in the case generation fails. One number emergency terminal box is provided centrally on each side of under
frame to facilitate charging of battery from external source. For BG AC coaches, 18 KW / 25 KW brushless alternators
are used. Two such alternators are used in AC-2T /AC-3T /Chair Cars and only an alternator is used in First AC coach.
Batteries of 800 / 11 00 AH capacity at 10 hr rating are used in I AC/ AC-2T / AC-3T /chair car of B.G. Coaches.
A schematic layout for 110 V DC system is given.
Three phase output from 4.5 KW alternator mounted on the bogie of coach is fed to the regulator cum rectifier for
rectifying the AC output to DC and regulating the output voltage at different speeds and loads. The output from
rectifier cum regulator on the underframe is brought through cables on the coach.
3.3 ALTERNATOR: 18 / 25 KW Brushless Alternator & Regulator (KEL make):
Principle of working of 18/25 KW brushless alternator is same as that of 4.5KW Alternator. 18/25 KW alternator is
used for AC coaches. The alternator with associated regulator delivers 18/25 KW (at a constant voltage of 135+/- 5%
from no load to 133 A) at all train speeds above 50 KMPH. Two machines are used for Ac 2T/chair cars and one
machine is used for IAC coach for:-
a) Charging the coach battery consisting of 56 cells of 800 AH capacity (1100 AH in new coaches).
b) Supplying the coach loads like compressors, lights and blowers.
3.3.1 PRINCIPLE OF OPERATION:The brushless alternator is 3 phase Inductor Alternator without any rotating
windings, commutator or slip rings. Both the field windings and AC windings are located in the stator.The AC windings
are distributed in 60 slots. The field coils are concentrated and forms into two slots. Each field coil spans half the total
number of stator slots. The rotor is made up of silicon steel laminations and resembles a cogged wheel. The teeth and
slots are uniformly distributed on the rotor surface (skewing the rotor axis). The alternator is equipped with two
numbers of 200 MM PCD 6 groove V pulley and is driven through an axle pulley of 572.6 mm PCD. V belts type - C-122
are used for drive.

3.3.2 ALTERNATOR DATA:
Output voltage 135 V5% on D.C. side, (97V, 3 phase AC)
Current 140/193 A (Max) on DC side
Cut in speed 550 rpm (30 KMPH with half worn wheels with pulley ratio
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200/572.6)
Maxm.speed for full output 930 rpm for 135 A at 135 V
(51 KMPH)
Maxm.speed 2800 rpm (156 KMPH)
Class of Insulation F
Resistance between field terminals. 7.3 Ohm.

3.4 RECTIFYING CUM REGULATING UNIT:
Rectifier-cum-Regulator Unit for 18 / 25 KW alternator KEL make (Fig. 14) has the following parts:-
3.4.1 POWER RECTIFIER (RP);-
This consists of six silicon diodes connected in three phase full wave bridge. The three phase output of the alternator
is rectified by these diodes to give a DC output at terminals +L and -C. Each diode is protected against transient surge
voltage by capacitor Cl. The whole bridge is protected against high frequency surges by capacitor C3. The DC output is
filtered by capacitor C2.
3.4.2 CURRENT TRANSFORMERS ; (CT1,CT2 & CT3)
The current transformers are used to sense the load current for the current limiter. When the primary winding of each
current transformer carries load current, the secondary winding feeds a three phase voltage to the rectifier RT2 in the
regulator rack.
3.4.3 REGULATOR RACK
The regulator rack consists of the following parts:
Excitation Transformer (E.T.): This is a one winding transformer with tapings for input and output. The transformer
steps down the voltage for the field coils. The output of the transformer is taken to the field through the Magnetic
Amplifier Before being rectified by field rectifier diodes. The transformer has five set of terminals. Terminals 14 and 15
- Input from Phase 14 and 15 of alternator. Centre tapping, terminal 19, goes to the -ve terminal for field supply.
Terminals 18 and 161 are the output terminals and go to the respective terminals on the Magnetic Amplifier.
Magnetic Amplifier (MA):
The magnetic amplifier forms the nucleus of the regulator circuit. It works on the principle of saturation of magnetic
core. The equipment has six sets of windings.
Two load windings 18-162 and 17-161
* Four control windings 10-11
26-27
20-40
29-30 (Not shown)
* (Of these only 10-11 and 20-40 are used in the circuit 10-11 for voltage and current control, and 20-40 for gain
control). The field current passes through the load winding and offers a variable impedance to the field circuit.

Field Rectifier Unit (D3-D4): The two silicon diodes D4 and D3 acts as a full wave rectifier for the field supply.
Thesediodes conduct alternatively, when the terminals 18 and 161 become positive with respect to thecentre tapping
19.The rectified current from the diodes is taken through the feed back winding 20-40 ofthe magnetic amplifier.
Terminals 20 and 19 form the +ve terminals form the field supply.
Free Wheeling Diode: In the normal circumstances, this diode D5 has no function. But should there be any reasonfor a
surge from the field circuit, which will have a polarity opposite to that of excitation, thisdiode will conduct, avoiding
creepage of the surge voltage to more important components likeMagnetic Amplifier.
Rectifier Bridges (RT1 and RT2):
Each bridge RT1 and RT2 is made up of six silicon diodes, connected for three phase full wave rectification. RT1
supplies the rectified voltage for voltage detector DT1, which is also the voltage developed by the alternator. RT2
rectifies the three voltage developed at C.T. secondary side and supplies to the voltage detector DT2.
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Voltage Detector DT1 & DT2:
These voltage detectors serve the function of providing necessary "error signal" for voltage regulator and current
limiting. It consists of a network of zener diode, potential divider and rheostat. The voltage drop across each
resistance can be adjusted by varying the resistances Rh1and Rh2. In the case of DT 1 when the output voltage
exceeds the rated voltage of the alternator, the voltage drop across R 1 will be sufficient to cause zener break down
and this will send a current through the control winding 10-11 of the magnetic amplifier. Similarly, in the case of DT2,
when the current reaches the pre-set present value, the voltage induced in the secondary of the current transformers
after rectification by RT2 will be sufficient to cause conduction of the zener diode and to produce the necessary error
signal to Magnetic Amplifier for current control. Zener diode starts conducting only at a designated voltage (zener
voltage). The voltage across the zener will be maintained even if the voltage input to the circuit is increasing. Thus, it
serves as a base for comparison.

Blocking Diodes (Dl and D2):

Diodes Dl and D2 are used to block the current from one zener to the other. Diode D1
preventcreepage of current from DT2 to DT l and D2 prevents current from DT1 to DT2.
This is achieved by the unidirectional property of diodes.
Working of Regulator:

The three phase output from the alternator is rectified by the bridge connected silicon diodes. The DC excitation to
the field is obtained by full wave rectification of alternating current provided through the field transformer and the
load windings of the magnetic amplifier. The voltage induced in the alternator winding is dependent on the speed of
revolution of rotor and on the excitation current. In the absence of voltage detector and magnetic amplifier, the
voltage of the alternator will rise indefinitely due to the positive feedback limited only by saturation of stator. But as
soon as the pre-set voltage is reached, the zener diode in detector DT1 conducts and sends a "Control current"
through the magnetic amplifier windings 10-11. The flux produced by the control current is in such a way that it
opposes the flux produced by the load windings, thereby increasing the impedance of field circuit. This increase in
field impedance reduces the field current and brings back the output voltage to the normal value required, The
current limiting is also achieved in a similar manner. When the pre-determined load current is delivered by the
alternator, the secondary voltage of the CT after rectification by bridge RT2 will provide the necessary "error signal"
for the magnetic amplifier. In this case also the voltage drop across the resistance R 1 will be sufficient to cause the
zener diode in DT2 to conduct. The control current from this also passes through the same control winding 10-11. The
effect of this control current is to retain the current at the limited value and to reduce the voltage. For a sustained
over-load, the generator voltage will fall to the battery voltage and relieve the alternator immediately, thereby
reducing the chances of damage due to the load.

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OPTIMISED REGULATOR



RECTIFYING CUM REGULATING UNIT
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4. TRAIN LIGHTING:
Train lighting is one of the important passenger amenities which influence the image of Railways. Although first train
ran on 16th April 1883 from Mumbai CST to Thane, train lighting system through axle driven dynamo pioneered by
M/s. J. Stone & Co. came to Indian Railways only by 1930. Dynamo / Brushless alternator driven from axle through flat
/ V belts, supplies the load when train is in motion and charges the batteries. The batteries supply the load when
train is stationary. Following systems for train lighting are presently in use
1) Axle driven system working on 110 V DC supply.
2) Mid-on generation with 415 V, 3 Phase generation AC 110 V utilization.
3) End on generation with 3 Phase 415 V generation and AC 110 V utilization
4) End on generation with 3 Phase 750 V generation and AC 110 V utilization
A decision has been taken that all coaches now being built will have only 110 V system.





4.1 AXLE GENERATION WORKING ON D.C. 110 V SUPPLY:
Three phase output from 4.5 KW alternator mounted on the bogie of coach is fed to the regulator cum rectifier for
rectifying the AC output to DC and regulating the output voltage at different speeds and loads. The output from
rectifier cum regulator on the underframe is brought through cables on the coach. The load is fed through four rotary
switches (RSW) and fuses connecting circuits LI, L2, F and SPM. LI feeds the essential lighting load like lavatories,
gangways, doorways and upto 50% of light in each compartment/bays corridor lights and night lights, L2 feeds
remaining lighting loads, F feeds the fan load and SPM feeds emergency feed terminals (EFT). An external battery
charging terminal (BCT) is provided to charge the battery from external charger, if battery is in rundown condition due
to failure of alternator.



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4.2 4.5KW ALTERNATORS (CGL make):

4.5 KW brushless alternator is of totally enclosed construction capable of developing
a constant voltage of 120V/30 V and is used for :-
a) Charging the coach battery;
b) Operation of lights, fans in the coach.
The alternator consists of two sets of windings viz. A.C. Winding and field winding, both accommodated in the stator.
The AC windings are distributed in the small slots and field windings are concentrated in two slots. Each field coil
spans half the total number of slots. The rotor, consists of stacked stamping, resembling a cogged wheel having teeth
and slots, uniformly distributed on rotor surface skewing the rotor axis. The core of the stator which is completely
embraced by the field coils will retain a residual magnetism if excited by a battery once. The flux produced by the field
coils find its path through rotor. When the rotor is rotated, the passage of rotor teeth and slots alternatively under the
field offers a varying reluctance path for the flux produced by the field coils. The flux which varies periodically links
with AC coils and induces an alternating voltage in AC coil. The frequency of induced voltage depends on the speed of
rotor. The magnitude depends on the speed of the rotor and level of excitation. The field is controlled through
regulator to attain desired output voltage. Alternator is mounted on the bogie or suspended from bogie. Bogie
mounting is called "Transom-mounting" and suspension from bogie is called "under-frame mounting". A suitable belt
tensioning arrangement is also provided to adjust belt tension as required. A belt tension indicator provided on non-
drive end shield serves to indicate the belt tension for under-frame mounted alternator. For bogie mounted
alternator belt tension indication is provided by compressed length of spring by indicator plate.

4.3 Rectifier-cum-Regulator units for 4.5 KW Alternator (CGL Make):
The Regulator-Rectifier unit has the following functions: -
i) Rectifying 3 phase AC output of alternator to DC using full wave rectifier bridge.
ii) Regulating the voltage generated by alternator at set value.
iii) Regulating output current at set value.
The main rectifier consists of six silicon diodes adequately rated and mounted on aluminium blocks secured on main
aluminium heat sinks whose cooling surface is adequately rated and exposed to air at the rear portion of box. Unit
comprises of following main components:-
a) Three phase bridge output rectifier consisting of six silicon diodes D1 to D6 mounted on aluminium blocks secured
to main heat sink. These aluminium blocks are suitably insulated from the main heat sink electrically by means of
nylon bushes/washers at the same time ensuring proper conduction and transfer of heat generated during operation.
b) Single phase full wave field rectifier diodes D16 and D17 mounted separately on heat sinks along with free wheeling
diode D18 suitable for the same.
c) Two sensing diodes (D19, D20 for current/voltage sensing) with zener diode (Z1) which acts as reference.
d) Current transformer (CT)
e) Main printed circuit board (PCB) with the control circuit and voltage setting potentiometer (P1) and current setting
potentiometer (P2).
f) Field transformer (FT)
g) Magnetic amplifier (MA)
Diodes D4 to D6 and Dl to D3 make up the positive and negative halves of the main three phase bridge rectifier which
receives the three phase AC input from the alternator and gives a DC output of DC + and DC-.
The current transformer (CT) senses in all three Phases. The secondary of which has a burden resistance (R5) to
convert the secondary current into voltage. This AC voltage is rectified by diodes DIG to D15 (bridge configuration)
and fed to the P2-R3 voltage divider chain. The voltage output is rectified (using D7& D9 diodes) and fed separately to
the R1-R2-P1-R4 voltage divider chain. These two sensed voltages are compared with the reference voltage of the
zener diode Z1 and subsequently fed to the control winding of the magnetic amplifier. This enables magnetic amplifier
to act as ON/OFF switch for controlling the alternator field current and in turn the alternator output voltage.

4.4 CHARACTERISTICS OF 4.5 KW ALTERNATOR & REGULATOR
Output 4.5 KW
Voltage 120V DC
Current 37.5 A
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Cut in speed 350 RPM (Approx 19 KMPH)
MFO 600 RPM (Approx 31 KMPH)
Max speed 2500 RPM (Approx 130 KMPH)
Mounting Transom Mounted
Drive V belts (4)
Insulation class
a) Armature H
b) Field H
Bearings
a) Driving End SKF Roller Bearing NU 311 or equivalent
b) Non driving end SKF Ball bearing 6309 or equivalent
Regulator Type Magnetic Amplifier
Voltage settings 110-140V DC marked in steps of 5V
Voltage regulator within +5% of voltage setting
Current setting 37.5 Amps
Current limiting + 15% 0%
Cut in : The minimum speed which the Alternator can pick up speed generation. There will be no output below
this speed.
MFO : Maximum speed for full output. Although generation picks up at cut in speed, for delivering full output,
speed is higher than cut in speed and is called MFO.



RRU panel has several disadvantages so it is now being widely replaced by ERRU or electronic rectifying cum
regulating unit.


4.5 ELECTRONIC RECTIFYING CUM REGULATING UNIT

Main features of ERRU with UVC:
Fast and reliable switching devices.
Alternator identifying facilities and
Auto setting of parameters such as output DC voltage, battery current, load current which in turn increase the life
of battery and the alternator itself.
Monitoring real time value of alternator voltage, load current, batteryAH (IN), AH(OUT) etc., through interface
fitted inside the coach.
Main advantages of ERRU:
Control circuit is Modular type design.
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BIRLA INSTITUTE OF TECHNOLGY, MESRA, RANCHI
Auto identification of alternator ratings and indications.
Auto setting of parameter of voltage, load current, Battery current, over voltage, over current and current limiting
for all the regulator of 4.5 kW, 18 kW and 25 kW.
UVC is interchangeable with all types of Electronic Regulators from 4.5 kW to 25 kW.
Close regulation of voltage +/- 2 V over the entire range of load and speed to have uniform charging of batteries.
Less voltage and current ripple on Battery Charging current.
Controlled Battery charging current to have longer life of batteries.

Rating and Setting :
(A) 25 kW Regulator:
Rating :
Voltage : 130 V
Full Load amps : 193 A
1-Hour rating amps : 222 A
Speed Range : 800 RPM to 2500 RPM.
Setting :
Normal : 127V +/- 0.5 V at 97 Amp. And at 1500 RPM
Over Load : 222 Amps at 120 V
Load Current : 230 Amps (Max)
Battery charging current: 110 Amps (Max.)
(B)4.5 kW Regulator:
Rating :
Voltage : 124 V
Full Load amps : 38 A
Speed Range : 550 RPM to 2500 RPM.
Setting :
Normal : 124V +/- 0.5 V at 19 Amp.
And at 1500 RPM
Facility available for setting: 120V,122V & 124V
Load Current : 42 Amp (Maximum)
Battery charging current: 24 Amp (Max.)

Main Components of ERRU :
The main components of the ERRU are as follows
Terminal Box
Power Unit
Universal Voltage Controller (UVC)
Static Over Voltage Protection (OVP)
Emergency Field Extension with interface
High Reliable Components
1. Half Effect Sensor.
2. ISOPACK Power Diodes.



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ERRU PANEL

4.6 BATTERIES

Conventional Lead Acid Cells for TL applications are governed by IS 6848.
Type of cells in use for train lighting and coach air-conditioning are as under :-
Capacity of battery in AH Type of coach at 27 Degree C at 10 Hr Rate and type of coach where generally used-
120 110 V, BG coaches
450 MG AC Coach
525 Jan Shatabdi Non - AC coaches
800 II AC BG Coaches (Old) (Under-slung type)
1100 II AC BG Coaches (new)/AC 3 Tier Coach

Constructional Features Main components of lead acid cell are :-
a) Positive Plates - Usually tubular construction is adopted. Positive plates are made up of a number of tubes which
contain active materials. Tubes have a large number of minute pores which allow the electrolyte to pass through
pores freely, while preventing any loss of active material.
b) Negative Plates - Usually consist of a lead grid into which active material is pressed. The grids are designed to
retain the active material in position.
c) Separators - Synthetic separators are used between positive and negative plates. The separators allow good
diffusion of electrolyte.
d) Container - is made of hard rubber with high insulating strength to resist acids.
e) Cell cover - is also made of hard rubber, resistant to acid having vent and level indicator holes.

The most commonly used battery pack in the coaches is voltage regulated lead acid battery whose specifications
and features are given below:-

Mechanism
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Safety Valve: When the internal pressure increases abnormally, the safety valve opens to release gas from
the cell to restore the normal pressure.
Flame Arresting Vent Plug: Provides with the explosion-proof filter constructed of aluminium oxide.
Container & Lid: Made of Polypropylene Co-polymer.
Positive Plate: With lead-calcium-tin alloy grid providing lower corrosion and less self-discharge rates.
Separator: Made of high Absorbent Glass Mat woven with excellent porosity (AGM type).
Negative Plate: With lead-calcium-tin alloy grid providing lower corrosion and less self-discharge rates.
Electrolyte: Dilute sulphuric acid without any impurity.

Features:
The Pure Lead-Tin range offers the customer the highest energy density of any lead acid battery anywhere. The
battery is constructed around a complex thin plate, pure lead-tin grid which packages more power in a smaller
space. The plates being made of high purity lead last longer, offering excellent life. The proven benefits of this
superior technology are high performance, quick recharge capability, high energy density and a long service life.
The 6V & 12V mono blocks are available in capacities ranging from 12Ah to 150Ah.



4.7 LIGHTING CIRCUIT
The lighting circuit cable (LC) form the under frame to junction box in the roof is divided into two circuits
through miniature circuit breakers of 35 A capacity for each of the circuits LI + and L2 +, Circuit LI + feeds the
essential lights which fulfill the minimum lighting requirements in a coach satisfactorily. These include lighting in
the lavatories, gangways, doorways and upto 50% of lights in each compartment /bays, corridor lights and night
lights. Circuit L2 + feeds all the lights other than essential and includes reading lights in I& II class AC coaches.







































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BIBLIOGRAPHY


www.irfca.org

www.wikipedia.com


www.irieen.org

www.electrical4u.com


Electrical Machines, V.K. Mehta

IRIEEN, Nasik publication journals on Train Lighting and Air
Conditioning






















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REMARKS