CHAPTER 1

1 INTRODUCTION OF NORTH WESTERN RAILWAY

The North Western Railway is one of the sixteen railway zones in India. It is

headquartered at Jaipur. It comprises four divisions: Jodhpur and reorganized Bikaner

division of the erstwhile Northern Railway and reorganized Jaipur and Ajmer

divisions of the erstwhile Western Railway. This zone came into existence on October

1, 2002. This railway comprises a total of 578 stations covering a total of 5449.29

route km out of which 2575.03 are broad gauge and 2874.23 are metre gauge.The

operating diesel sheds of NWR are ABR (Abu Road)which holds WDM2's and

Bhagat Ki Kothi (BGKT) Jodhpur which holds WDM2 WDG's WDP4's WDM3A's

which are broad gauge locomotives ,and Phulera at Jaipur which use to hold YDM4's

which are meter gauge locomotives .NWR even holds international rail service Thar

express Jodhpur to Munabao.

Fig 1.1 india railway jone

1 ITM/EE/2010/062

Fig1.2 north western railway system map

Ajmer division is one of the important divisions of North-Western Railway. It has 2 ITM/EE/2010/062

three major work shops which have got second position in Western Railway

Ajmer Group of workshop

1- Diesel loco and wagon Workshop

2- Carriage Workshop

3- Electrical Workshop

4- General Store

5- Personal Department

6- Supervisor Training Centre

7- CMT

8- EDP Centre

9- Workshop Accounts

My training are in 2 most important workshop.

Most important workshop:-

Carriage Workshop

Electrical workshop

CHAPTER 2

3 ITM/EE/2010/062

2 RAILWAY POWER HOUSE :-

Railway Power House is situated at “NORTH WESTERN RAILWAY D.E.E, DRM

OFFICE Ajmer“.it is 33/11 K.V. SUB STATION. a 33 KV feeder is given to the

power house from Rajasthan state electricity board [R.S.E.B] and a two 500 KVA

D.G. SET ,1750 KVA D.G. SET were also installed In which some modern oil circuit

breaker [O.C.B] were installed. This power house supplies the electrical energy to

different parts of Ajmer division with the rate of 4.5 Lakh Unit /month.

2.1 Classification of Railway Power House

Now electrical power house can also subdivided into three parts for better

understanding.

a) Yard

b) Control room

c) 1750 K.V.A D.G. set room

2.2 Yard:-

Yard is a basically a 33/11 K.V sub station and its line diagram is shown on the left

hand page 33 K.V. feeder has come here from R.S.E.B. Madar by crossing Nasirabad

road. Different safety equipment are arranged in this feeder which are clearly shown

in schematic diagram.. After these arrangements this 33K.V. feeder is connected to 33

K.V. O/H Bus Bar which are placed horizontally in the yard. An earth switched is also

arrange in 33 K.V. feeder. Three feeder have taken from 33 K.V. B.B. after isolating

switch. Each feeder are arranged with different safety equipment as shown in figure.

4 ITM/EE/2010/062

Fig 2.1 single line diagram of railway power house

2.3 Equipment Used In Railway Power House Substations

1. Lighting Arrester

2. Isolator

3. Potential Transformer

4. Current Transformer

5. Circuit Breaker

6. Protective Relay

7. Bus Bar

8. Insulator

9. Fuses

10. Arching Horn

5 ITM/EE/2010/062

11. Transformer

12. Earthing

13. Earthing Transformer

14. Control cables

15. Oil Filter

16. Battery Charger

17. P.F. Improvement Unit

18. Stand By Units

Fig 2.2 lighting arrester

6 ITM/EE/2010/062

2.3.1 Lightning Arresters

The most common device used for protection of the power system against high

voltage surge is the surge diverter which diverts the incoming high voltage wave to

earth. Such a diverter alternatively called lightening arrester.

Advantage

a) They are providing very efficient protection against surges.

b) They operate very rapidly taking less then a second.

c) The impulse ratio is practically unity

Limitation

a) They may fail to check surges of very strip wave front from reaching the terminal

apparatus.

b) Their performance is adversely affected by the entry of moisture in to the enclosure.

Fig 2.3 potential transformer

2.3.2 Potential Transformer

7 ITM/EE/2010/062

Potential transformer which step down the voltage at system to sufficiently low

values, are necessary on every power system for –

a) Indicator of voltage condition

b) Metering of supply for exchange of energy

c) Relaying and synchronizing

The PT is employed far voltage above 380 volts to feed the potential coil metering

and indicating instrument. The primary winding of PT is connected to the main bus

bar of the switch gear installation and to the secondary winding various indicating and

metering instrument are connected. It is located b/w the CT and isolator.

Fig 2.3 Potential Transformer

Application

PT's are used for the measurement and protection accordingly these are either

measuring protective type voltage transformer. These may be single phase or three

phases.

8 ITM/EE/2010/062

fig2.4 current transformer

2.3.3 Current Transformer

Measuring of A.C. one of the most frequent operation not only of its inherit but also it

is necessary in determining other parameter of electric circuits. A current transformer

is intended to operate normally with the rated current of the network flowing through

the primary winding, which is interested in series network. The secondary of circuit is

connected to the measuring instrument and relays supplies a current which is

proportional to & in phase with current error and phase displacement inherent in the

design of the circuit. Construction

9 ITM/EE/2010/062

Fig 2.4 Current transformer

The C.T. basically consist of core on which are wound a primary and one of two

secondary winding. The primary is directly inserted in power circuit (The circuit

current is to be measured) and to the secondary winding. The indicating and metering

instruments are connected when the rated current of C.T. flows through its primary

winding, a current of 5 Amp. will apart in its secondary windings. The primary

winding usually a signal turn winding and numbers of turns as the secondary winding

depend upon the power circuit to be measured.

2.3.4 Circuit Breaker

10 ITM/EE/2010/062

Circuit breaker plays on important role in the design and performance of a power

system on that these are the key piece of apparatus protecting the system and that

ensure that continuity of supply. From consideration of cost the circuit breaker

represent a major item & is perhaps only to generator & transformer.

Necessary Function

a) Carry continuously maximum current of the system.

b) Make and break the circuit under faulty and normal operating condition.

c) It may also happen many times that a circuit breaker is closed the system when the

faulty conditional persist. It should not damage or create condition. It should not

cause damage to other equipment on the system. In railway power house minimum oil

circuit breaker are used.

Fig2.5 M.O.C.B.

2.3.5 Minimum Oil Circuit Breaker

It acts as an arc quenching medium and it insulates the live part from earthed. It has

been found that only a small percentage of oil is actually used for arc extension while

the major part is utilize for insulation purpose. This action concentrates the oil to pass

through a central hole in the moving contact and result in forcing the series of oil

through the respective passage of the tabulators.

11 ITM/EE/2010/062

Fig 2.5 Minimum Oil Circuit Breaker

Advantage

There is a reduce risk of fire.

It requires lesser quantity of oil.

It requires smaller space.

Maintenance problems are reduced.

Disadvantage

a) Due to smaller quantity of oil the degree of combustion is increased. There is a

difficulty in removing the gases from the contract space in time.

b) The dielectric strength of the oil deteriorates rapidly due to high degree of

carbonization.

12 ITM/EE/2010/062

2.3.6 Protective Relay

In a process power system consisting of generator transformer transmission as

distributive circuit. It is in evil able that sooner or later some failure will occurs on

any part or the system. It must be quickly dependent and disconnect the circuit. A

protective relay is a device that detects the fault and indicates the operation of the

circuit breaker to isolate the defective element from the rest of the system.

A typical relay circuit is shown in the figure. This shown one way of 3-phase system.

The relay circuit connection can be dividing in three parts.

a. First part is primary winding of a current transformer, which is connected in series

with the line to be protected.

b. Second part consists of secondary winding of CT and relay operating coil.

c. Third part is the tripping circuit which consists of a source of supply. The trip coil of

the circuit breaker and the relay stationary contact.

2.3.7 Transformer

A Transformer is a static piece of apparatus by means of which electric power of one

circuit is transferred into electric power of the same frequency in another circuit. It

can rise up or down the voltage in a circuit but with the corresponding decrease or

increase in current. The physical basic principal of transformer is "Mutual induction"

but two electric circuits linked by a common magnetic flux. In its simplest form it

consist of two induction coils which are electrically separated but magnetically linked

through a path of low reluctance. The two coil possesses mutual inductance.

2.3.8 Power Transformer

Power Transformer have a rating above 200 K.V.A. and are used in generating

stations and are used in sub station at each end of a power transmission line for

stepping up or stepping down the voltage. They may be either 1 or 3 units. They

are put in operation during load periods. Therefore power transformer should be

designed to have maximum efficiency at near full load. Power transformer are

13 ITM/EE/2010/062

designed to have considerable greater leakage reactance than is permissible in

distribution transformer as in the case of power transformer inherent voltage

regulation is less than the current limiting effect of higher leakage reactance.

2.3.9 Main Parts of Transformer

a. Transformer Tank

b. Breather

c. Conservator

d. Explosion Vent Plug

e. Temperature Indicator

f.Fins

g.

Fig 2.6 MAIN PARTS OF TRANSFORMER

14 ITM/EE/2010/062

2.3.10 Distribution Transformer

Transformers up to size of about 200KVA used to step down the distribution voltage

to a standard service voltage or from transmission line voltage to distribution voltage

are known as Distribution transformer. They are kept in operation all the 24 hours a

day whether they kept any load. Energy is lost in iron losses throughout the day while

the copper losses account for loss in energy when the transformer loaded. Therefore

distribution transformer should have their iron losses small as compared with full load

copper losses. In other words they should be designed to have maximum efficiency at

a load much lower then full load.

15 ITM/EE/2010/062

CHAPTER3

3 DIESEL POWR STATION :-

Diesel Power station is the most important part of Railway Power House. We can say

it, an energy power sources for railway, when R.S.E.B. supply is failure due to any

reason then this set is used to feed the supply to the Loco workshop and Carriage and

Wagon shop. This power station is installed here due to its following advantages –

1. Diesel is used as a fuel in this plant which is easily available in Ajmer as

compared to coal.

2. The design & installation of this plant is very simple.

3. The space requirement for this plant is less.

4. Less staff is required to operate this plant because many functions are controlled

by panel board.

Different parts of Diesel Power Plant

16 ITM/EE/2010/062

3.1 Diesel Engine

Diesel engine is the main and heaviest part of Diesel Power system. The mechanical

data’s of diesel engine is given below:

Specification

Engine No.

B.H.P.

Type

No. of cylinder

Bore

Stroke

1.2007 021330

2496

16V9x 10½ 251 B Max. Crank Shaft

16

9”

10 ½

17 ITM/EE/2010/062

Table 3.1:- List of specification of diesel engine

The main function of Diesel Engine is to produce a rotating mechanical power. This

mechanical power is used to rotate the alternator shaft and after rotating action it

generates the electric power. It is a multi cylinder engine. There are 16 cylinders in

the engine. Each cylinder is mounted on the engine with every small inclination from

its vertical axis. 8 cylinders are mounted on the right of the engine’s horizontal axis

and other are mounted towards the left side.

From the front side the cylinder is like ‘V’ shape. So this is called ‘V’ engine. In this

type of engine diesel is used for fuel. This engine is air injection type, so air is

compressed through a compressor and stored in air tanks. Compressed air and fuel is

supplied to the fuel valve. This valve is open at a pre setter time. When this valve

opens, the blast of compressed air takes the fuel in cylinder with itself and combustion

is completed in the cylinder. This action produces an energy which moves the crank

shaft. The crank shaft motion which given by cylinder is in cylinder order.

3.1.1 Fuel System

First of all, the fuel is filled in a storage tank. Before filling the fuel in the tank, it is

filtered by a strainer so suspended impurities can be removed with the help of pump,

this oil is given to the injector. In this way the diesel is filtered again.

3.1.2 Air injection System

This diesel engine is air injection type. So compressed air is required in this diesel

power station. For this purpose an arrangement of air compressor and air tanks are

made. This air compressed is driven by a 3 phase A.C. induction rotor.

3.2.1 Exhaust System

This system is provided to discharge the exhaust gasses in the atmosphere. Exhaust

system of each cylinder is connected to a main exhaust pipe. This exhaust pipe not

only reduces the pressure in exhaust but also reduce the noise.

18 ITM/EE/2010/062

3.2.2 Cooling system

The cylinder of diesel engine may be heat up during its working condition. So a

cooling system is provided to cool the engine. In this system, chilled water is

continuously flowed in the cylinder jacked. This water absorbs the heat from the

cylinder and gets heat up. This hot water is taken in a heat exchanger. It cools the hot

water and this cool water is again supplied to engine.

3.2.3 Lubricant system

To reduce the fiction losses, lubricant system is used. In this system the lubrication oil

passes through a strainer & filter to remove the impurities. Now this lubricant is sent

in the engine from a pump.

3.3 Starting system

In this Diesel power plant battery & compressed air is used to start the engine. Above

1750 KW D.G. sets are started with this method. The diesel engine is stored with the

help of battery driven motor. At the starting period some deflection is given to the

shaft of diesel engine through a gear with the help of this starting motor.

19 ITM/EE/2010/062

Fig 3.2 alternator

3.4 Alternators

It is also a measure part of the diesel power plant. Alternator shaft is coupled with

diesel engine. It has large diameter and short axial length

3.5 Working Principal of 1750 KW D.G. Set

When Diesel Engine is started, it drives the Alternator shaft also. The exciter is also

belted from the rotor shaft induce some e.m.f. which is supplied to the rotating field

winding of Alternator. A constant flux has set up. A constant flux will links with

stationary armature winding. When the speed of engine is increased all these factor

increase the induce e.m.f. by Alternator diesel engine and exciting current through the

exciter is controlled from control panel. The desired frequency is gotten by the

variation of speed of diesel engine. When required values of electrical quantities are

generated, the supply is fed to the main control Railway Power House.

20 ITM/EE/2010/062

3.6 Starting Instruction

All fuel oil, lubrication oil jacket water & raw water valve should be in open

condition.

Start raw water pump from old Power House.

Check air pressure in air tank and it should be minimum 200 P.S.I. in both tanks.

Start pre lubricant oil pump and wait till “low” oil pressure indicator vanishes from

control panel.

3.7 To Start D.G. Set

Open valve of both the air tank.

Switched ‘ON’ all the AC & DC auxiliary supply board near main O.C.B.

All 5 no. rotary switches provided on Control Room panel for air compressor, Crank

Shaft, exhaust motor to be ‘ON’ position.

Push air starting switch provided at the engine of the governor.

Engine is now in starting condition.

CHAPTER 4

21 ITM/EE/2010/062

4 TRAIN LIGHTING & CARRIAGE MOTORS:-

Introduction

Carriage and Wagon Shop is one of the most important workshop of the western

railway. Here the poll of the meter gauge and board gauge coaches of carried out even

the repairing and over hauling of the coaches of tourism trains like palace on wheel &

royal oriented luxury of western railway express is carried out these are most

important and costly trains here poll of MG & BG wagons are also carried out.

Expect these work, this work shop also supplied the parts and other equipment of the

coaches to other division of the western railway. In carriage and wagon shop, the

electrical repairing of the coaches is done in following department:-

1. Train lighting

2. Carriage motor

4.1 Train Lighting System

On the basis of generation following train lightning system are used :-

1. EOG (End On Generation)

1 Generating Voltage 415 V

2 Generating Voltage 450V

2. Mid On Generation (MOG)

3. Self Generating System0

1 V DC (from Dynamo)

2 24 V DC (from Alternator)

3 110 V DC (Alternator)

22 ITM/EE/2010/062

4.1.1 End on Generation

In this type of system electricity is generated in power car instead of coach. This

system is used in trains having AC coaches like Rajdhani express, Shatabdi

express etc. In this system two power cars are installed on the basis of

generating voltage. Two type of power cars are used

1) 415V, 3 Phase AC

2) 750 V,3Phase AC

In these days 750V, 3 Phase AC systems are preferred. In 415 V AC capacity of

alternator is 160KVA, 220 KVA, 250 KVA etc. while in 750 volt system 500KVA

alternator is used. This alternator is coupled to 390 BHP. 1500 RPM diesel

engine. In each power car there are two DG sets so there are four DG sets in two

power cars. Electricity generation from alternator is given to individual coach

from two feeders. These feeder are provided with overload, earth fault and fuses.

Alternator is also provided with overload, earth leakage, under voltage

protection etc.

23 ITM/EE/2010/062

For excitation of alternator 24 V, 320 AH capacity of battery and battery charger

are given in power car. This battery is also used for emergency light in power

car. In each coach a step down transformer 415/110V is given.110V AC used for

fans and lights. AC plant motors are operated on 415 V 3 Phase AC supply. In

each coach 24 V 90 AH batteries is given for emergency light.

Merits

1. This system is much reliable

2. Illumination is good

3. Voltage drop is less

4. Low maintenance

Demerit

1. Running cost is high

2. A power car has to work when train is at halt.

3. More diesel is used

24 ITM/EE/2010/062

Fig 4.2 mid on generation

4.1.2 MOG (Mid On Generation)

This train lightning system is used on small branch lines, hill area. In this system

power car is used in the middle of all coaches therefore it is called as Mid On

Generator. In this trains maximum 13 coaches are used with power car.

25 ITM/EE/2010/062

In power car two DG sets of 30 KVA capacity each are used which generates 415

V, 3 AC diesel engine of 41,43,47BHP 1500RPM air cooled are used. Only one

alternator is used at a time. Second is used as a stand by for alternator excitation

24V 320 AH battery and battery charger are given. 415V generated by

alternating is step down to 110 V 3 A C 50Hz by 30 KVA step down transformer.

This 110 V 3 is given to bus bar. From bus bar this power is supplied to

particular coach. Feeders of 70 Sq. mm and 120 Sq. mm are mostly used for light

and fan load separate feeders are used.

Merit

1. It is more reliable from self generation

2. Low maintenance

Demerits

1. We can not use more than 6 coaches on one side of power as voltage drop

below 5.5 V is not permit able.

2. Creates disturbance to nearby passengers.

3. Can only use less number of coaches.

26 ITM/EE/2010/062

Fig 4.3 S.O.G.

4.1.3 Self Generation System

a. Generating Equipment

In self generating coach the apparatus used for generating electricity are known

as generating equipment. In old T/L system dynamo was used but in modified

system brushless alternator are used. Alternator produces AC which is converted

into DC rectifier cum regulator and this DC is given to coach load and battery.

Following alternator are used in coaches.

1.

2.

3.

4.

3 KW , 130 V , 100 Amp

4.5 KW , 120 V , 150 Amp

3 KW , 120 V , 150 Amp

Meter Gauge , Non AC Coach

Broad Gauge , Non AC Coach

Meter Gauge , Non AC Coach

27 ITM/EE/2010/062

5.

6.

12 KW , 120 V , 100 Amp

18 KW , 130 V , 133 Amp

22.75 KW / 25 KW , 130 V

Meter Gauge , AC Coach

Broad Gauge , AC Coach

Broad Gauge , AC-3 tier Coach

Table 4.1:- List of generating equipment

4.2 Train Lighting

Basically two types of apparatus are use for train lighting they are:-

1. Alternator 110 V (A.C.)

2. Battery 110 V (D.C.)

All the apparatus such as alternator battery & other useful apparatus are assembled

inside the logs. Alternators have coupled with bogeys shaft by the belt or pulley

arrangement. It generates 110 V (constant voltage) whenever train runs on the track,

But it generates this voltage after some time when train runs in is average speed.

Batteries and alternator sets are connected from the regulating panel which is installed

in the bogies. It disconnects the load circuit of coach from the battery when alternator

gives their proper voltage.

Batteries are use in case of train is not running on the track or in standing condition on

the plate from few minutes. The batteries output is also 110 V but it has DC in the

nature because alternator gives 110 V, 3 phase A.C. voltage so rectifier circuit is used

to convert it into D.C supply. This rectifier circuit is arranged in the regulating panel.

Besides the load circuit alternator generating voltage are also used for charging the

batteries.

28 ITM/EE/2010/062

This charging system of battery has controlled from the regulating panel. Whenever

battery reaches their rated voltage after than they have automatically disconnects from

the alternator circuit.

Different type of protective devices is used in the regulation panel. It disconnects the

battery circuit. From the alternator in case of over change and it is also used for other

protection from the minor and major part.

4.2.1 Alternator Section

It is also a measure part of the diesel power plant. Alternator shaft is coupled with

diesel engine. It has large diameter and short axial length. The main data’s of

alternator is follows:

The alternator contains three parts. They are:

1. Stator

2. Rotor

3. Exciter

The constructional feature and working of each part is as follow one by one on

next page.

1. STATOR:-

It is the starting part of an alternator and consist of cost iron frame, which

support the armature core, hawing itoh, and its inner portion is used to carry the

armature winding. It has large diameter and axial length. Its outer portion is just

like a cylinder and inner portion is known as stator core. Stator core is made of

lamination special magnetic iron or stated alloy. Each lamination are of insulated

with varnish and are steamed out in segments.

This stator is used the losses due to:- eddy current. Its slots are made in the inner

part of stator for housing the armature conductor slots. They ma be wide open,

semi open or closed type but closed type slots are rarely used.

29 ITM/EE/2010/062

The armature winding in the alternator are open i.e. there is no closed path for

the armature current in the winding itself. One of each phase winding is

connected to the natural point and other end is brought out chain winding is

used in this alternator. It may be single layer or double layer.

2 ROTOR:-

Rotor is a moving part of alternator. This is salient pole type. In AC generator,

rotor carrier the field winding. Constructionally it is looked like a fly wheel

alternator and rotor fined to outer rim.

It had a large number of projecting pole s having there core bolted on to a heavy

magnetic wheel. This is made of cast iron or steel alloy. The pole and pole shoe

are laminated to minimize heating & losses due to eddy current field winding in

wounded around the pole core and two slip rings are mounted on the floor. The

terminal of field winding is commeasures with the slip rings. Two brushes are

also arranged on slip ring to supply the DC to the field windings.

3 EXCITER:-

It is a DC shunt generator and belted on the staff of alternator. The main function

of exciter is to excite the field magnets i.e. to supply DC the field winding because

the field magnets are rotating; this current is supplied through two slip rings

which is mounted on the rotor. The output voltage of exciter is 65 volts.

4.2.2 Specification of Alternator

1. Type AK132M53

30 ITM/EE/2010/062

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

R.P.M.

Power Factor

Phase

Power in KW

Power in KVA

Current in Amp.

No. of Poles

Excitation Voltage

Excitation Amp.

Voltage

Connection

Lubricant

Maker

1000

0.8

3 Phase

1750Kw

2187.5KVA

114.8A

6

65Volts

390A

11KV

Star Connected

DTE Light

BHEL Hyderabad

Table 4.2:- list of specification of alternator

4.2.3 Brush less Alternator

It is a 3 phase induction machine. It has no winding on its rotor. It has no slip

ring, commutator & brushes etc. It is dust proof and water proof machine. On the

circumference of rotor teeth & slots are made, as rotor is of salient pole type the

air gap changer between rotor and stator. The flux induced in alternating type

which is cut by 3 phase A.C. winding & thus E.M.F. produce in winding.

31 ITM/EE/2010/062

On the shaft of alternator i.e. on driving side a pulley is fixed. The diameter of flat

belt pulley is 140mm and for adjusting the belt tension arrangement is given.

This alternator work with rectifier regulator panel. The o/p of alternator can be

adjusted by adjusting the field.

4.2.4Alternator (brush;ess)Specification

Rating

Volt

Ampere

Frequency

4.5 K.W.

30 V

120 A

50 Hz

Table 4.3:- List of specification of alternator(brushless alternator)

Feature of Alternator

1. Light in weight.

2. Reliable source of A.C power.

3. Suitable control by static regulator.

4. Long life and minimum maintains.

4.3 RRU / ERRU (Rectifier Regulated Unit)

To start the fan, light in a Indian rail battery system are used. The o/p of a 3 phase AC

of the alternator is change in DC with the help of RRU (rectifier regulated unit) and

new technical electronic based ERRU are used, 32 ITM/EE/2010/062

Function of RRU

1. AC to DC for battery charging.

2. Control the alternator o/p by the field excitation.

3. To control the o/p voltage according to o/p current.

Fig 4.3 battery (cut of section)

4.4 Train Lighting Cells (Battery Section)

Train lighting cells are secondary cells such as “lead acid cell” .In a charged lead acid

cell the positive active material consist of lead peroxide [Pbo2] and the negative

spongy lead [ pb ]. Dilute sulphuric acid [H2So4] serves as a electrolyte.

33 ITM/EE/2010/062

The overall reaction inside the cell during discharge the charge are represented most

conveniently be a reversible equation as follows.

Pbo2 + Pb + H2SO4 2 PbSO4 +2H2O

4.5 Fans used in trains

There may be of three main types of fans i.e. DC fans, A.C. fans, DC / AC fans. An

electric fans is simply an electric motor to which the blades are fixed so that when the

motor of the fan rotates the blades throw the air.

In the train bogies generally two types of fans are used

1. 110 V A.C. fans

2. 24 V D.C. fans

4.5.1 24 V DC Fans

The DC fans are of DC series motors in which the rotating part armature is connected

in series with the stationary part. When the field is set up in the field winding which

experience a force in the armature tending to move it at right angle to the field the

blade attached with the shaft of the armature displaces the air.

4.5.2 110 V AC Fans

The same principal applies to the AC fans but there is some difference in the

construction of AC Fans than DC Fans that the rotating part of the A.C. fans is called

a rotor and stationary part is called a stator. In the case of A.C.

Fans mainly two types of single phase motor are used. These all types of motor work

on the principle of induction motor

1. Shaded pole type motor

2. Capacitor run motor

34 ITM/EE/2010/062

4.6 Scale of Illumination

4.6.1 Quantity of lamp for various coaches

1.

2.

3.

4.

5.

First class

Second class

Postal van

Dining

Corridor first class

16 lamps

40 lamps

30 lamps

16 lamps

11 lamps

Table 4.4:- List of quantity of lamp for various coaches

4.6.2 Lamp power consuption

35 ITM/EE/2010/062

1.

2.

3.

4.

5.

6.

Night lamp fitting

Cooling fitting gallery

Cooling light passage

Postal van dining

Reading light

Bulbs (BG), Bulbs(MG)

20 Watt.

20 Watt.

30 Watt.

30 Watt.

10 Watt.

110V/ 25 Watt, 24 V/20 Watt

List4.5 List of lamp power consumption

4.7 Carriage motors

These are the main section of railway where the maintenance and repair of A.C.

machine windings is made by workers. Different types of machine came here for

maintenance and rewinding which are as follows:-

1. A.C. Induction motor

2. D.C. Motor

3. Transformer

4.7.1 Induction Motor

Induction motors are two types

1. Slip ring Induction motor

2. Squirrel cage Induction motor

An Induction motor consists of two main parts:-

1. Stator 36 ITM/EE/2010/062

2. Rotor

1 Stator

Stator is a stationary part of an induction motor. It is cylindrical structure, built up of

dynamo grade lamination. The laminations are either 0.35 or 0.50 mm thick. Stator

carries a three phase winding and is required a three phase supply. It is wound for a

definite no. of poles the exact poled being determined by the requirement of speed.

Greater the no. of pole, lesser the speed and vice-versa. When three phase supply is

given to stator winding. It produces a flux, which is of constant magnitude but which

rotates at synchronous speed. This revolving flux induces an emf in the rotor by

mutual inductance.

2 Rotor

Rotor is the rotating part of induction motor. Various type of rotor are used in the

induction motor such as:-

1. Squirrel cage wound rotor

2. Double Squirrel cage wound rotor

3. Slip ring rotor

a. Squirrel Cage Wound Rotor

Mostly Squirrel cage wound rotors are used in induction motor, because this type of

rotor has the simplest and most rugged construction. The rotor consist of a cylindrical

laminate core with parallel slot for caring the rotor conductor. In a Squirrel cage

wound rotor, the rotor bars are permanently short circuited. Hence it is not possible to

add any external resistance in series with the rotor circuit for starting purpose.

b. Double Squirrel Cage Wound Rotor

37 ITM/EE/2010/062

Double Squirrel cage wound rotor has two slots first slot have made in inner

circumference that are full closed slots and other slots have made on the periphery of

rotor that are half closed slots low resistance and high cross section copper code are

wound in the full closed slots and after then its short circuited in both side with a

conductor. Winding method is performing just like full closed slots but these are high

resistance and low cross section bars for winding.

c. Slip Ring Rotor

Starting torque of these motor are greater than Squirrel cage wound rotor when we

drive motor. The starting condition high resistances winding of motor are used but

after coning in its synchronous speed then only work low resistance winding.

The slip ring motors are used where high starting torque is required .For instance

1. In the hoist,

2. In the cranes,

3. For power hammer,

4. For lift,

5. For battle ship purpose.

4.7.2 D.C. motor

D.C. machine can be works as generator, motor, breaks. In generator mode the

machine is driven by a prime motor with mechanical power converted into electrical

power. While in the motor mode the machine drives a mechanical load with the

electrical power supplied converted into mechanical power. In the break mode

( which functions as a motor before the applications of breaking action) the machine

works as a generator & the electrical developed is either pumped back to supply as in

regenerative breaking or dissipated in the machine system the machine deaccelerated

on account of the power dissipated by it and therefore produces a mechanical braking

system. 38 ITM/EE/2010/062

The D.C machines used for industrial application have essentially three major parts

1. Field system

2. Armature

3. Commutator

1. Field System

Field system is located the stationary part the machine called stator. The field system

is designed for provides the necessary excitation for operation of machine.

The stator of D.C. machine comprise of:-

1. Main poles.

2. Inter poles.

a. Main Poles

These poles are designated to produce the main magnetic flux.

b. Inter Poles

These poles are placed between the main poles and are design to improve

commutation condition to ensure spark less of machines. Interpoles are not use in very

small machines.

2. Armature

The Armature is the rotating part of a D.C. machine where processor of electro

mechanical comes. It is a cylindrical shape which rotates between the magnetic poles.

The armature consists of:-

1. Armature core with slot

2. Armature winding

3. Commutator

39 ITM/EE/2010/062

The commutator is mounted on the rotor shaft at a D.C. machine and it performs with

the help of brushes. A mechanical arrangement converts A.C. into D.C. in case of

generator and D.C. to A.C. in case of motor.

40 ITM/EE/2010/062

CHAPTER 5

REFRIGERATION & AIRCONDITIONING & WITH RECTIFIER

5.1Refrigeration:-

Refrigeration is a process in which work is done to move heat from one location to

another. This work is traditionally done by mechanical work, but can also be done by

magnetism, laser or other means. Refrigeration has many applications, including, but

not limited to: household refrigerators, industrial freezers, cryogenics, air

conditioning, and heat pumps.

5.2 Air conditioning:-

Air conditioning is the removal of heat from indoor air for thermal comfort. In

another sense, the term can refer to any form of cooling, heating, ventilation, or

disinfection that modifies the condition of air. An air conditioner (often referred to as

AC or air con.) is an appliance, systems.

5.3 Refrigeration cycles:-

Refrigeration cycle is a process that removes heat from indoor evaporator to outdoor

condenser units.

5.4 Principle of refrigeration cycle: -

Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and

mathematical models for heat pumps and refrigerators. A heat pump is a machine or

device that moves heat from one location (the 'source') at a lower temperature to

another location (the 'sink' or 'heat sink') at a higher temperature using mechanical

work or a high-temperature heat source. Thus a heat pump may be thought of a

"heater" if the objective is to warm the heat sink (as when warming the inside of a

home on a cold day), or a "refrigerator" if the objective is to cool the heat source (as

41 ITM/EE/2010/062

in the normal operation of a freezer). In either case, the operating principles are

identical. Heat is moved from a colder place to a warmer place.

The components of the gas refrigeration cycle are very similar to the vapor

compression cycle. The gas flows through the compressor where its pressure and

temperature becomes very high. It then flows into the heat exchanger, which performs

the function similar to the condenser in the vapor compression cycle, except that there

is no change in the phase of air or gas. In the heat exchanger the air gives up heat, but

its pressure remains constant.

The high pressure and medium temperature air then enters the throttling valve (also

called expander), where its pressure is reduced suddenly and due to this its

temperature also becomes very low. The low temperature and low pressure gas then

enters the other heat exchanger (also called refrigerator) which performs the function

similar to the evaporator in vapor compression cycle. The gas absorbs the heat from

the substance to be cooled and becomes hotter, while the substance becomes cooler.

There is no change in phase of the gas in this heat exchanger. The high pressure and

high temperature gas then enters the compressor where the cycle repeat.

42 ITM/EE/2010/062

43 ITM/EE/2010/062

5.5 Components of Refrigeration unit:-

Refrigeration cycle has five basic components to work:

1. The evaporator unit

2. The expansion valve

3. The compressor

4. The condenser

5. The copper refrigerant tube (a tube that connects these air conditioner

parts)

(1) The evaporator unit: -

In the Refrigeration cycle evaporator is a heat exchanger that absorbs heat into the air

conditioner system. The evaporator does not exactly absorb heat! It’s the cooled

refrigerant fed from the bottom of the evaporator coils absorb the heat. The liquid

refrigerant usually flows from the bottom of the evaporator coils and boils as it moves

to the top of the evaporator coils. The reason it’s fed from the bottom is to ensure the

liquid refrigerant boils before it leave the evaporator coils. If a refrigerant was to fed

from the top, the liquid refrigerant would easily drop to the bottom of the coils before

it absorbs enough heat and boil. If evaporator was too feed liquid refrigerant into air

conditioner compressor; it will shorts the air conditioner compressor.

The air conditioner evaporator has three important tasks:-

(1)Its absorb heat.

(2)Boils the entire refrigerant to vapor aqua saturated vapor.

(3)Superheat.

(2) Expansion Valve:-

44 ITM/EE/2010/062

All expansion device or metering device has similar function (to some extent); it’s

responsible for providing the correct amount of refrigerant to the evaporator. This is

done by creating a restriction within the thermostatic expansion valve. The restriction

causes the pressure and temperature of the refrigerant entering the Evaporator to

reduce.

The refrigeration cycle diagram above has a thermostatic expansion valve. This

expansion device has

(1) Remote Bulb

(2) Capillary Tube

(3) TXV Body

Thermostatic expansion valve has other components besides these three. However,

they are not important right now.

TXV provides the correct amount of air conditioner refrigerant to the evaporator by

using a remote sensing bulb as a regulator. The remote sensing bulb and capillary tube

has a refrigerant inside.

As you can see in the refrigeration cycle diagram above, the remote sensing bulb is tie

with the suction line. The temperature from the suction line transfer heat to the

sensing bulb through conduction. Sensing bulb responds to the temperature of the

suction line and as a result, it decreases or increases the temperature and pressure

inside the sensing bulb due to suction line temperatures. The sensing bulb also has a

diaphragm on the other end. This diaphragm is with the TXV body. The diaphragm is

the device that pushes or releases the needle from the valve seat.

(1) The compressors:-

The air conditioning compressor is known as the heart of the air conditioner units. It’s

one of the divided points between high and low side. As you can see in the

refrigeration cycle diagram; the compressor has a refrigerant inlet line and refrigerant

45 ITM/EE/2010/062

outlet line. The compressor inlet lines are known as:

(1)Suction pressure

(2)Back pressure

(3)Low side pressure

The compressor outlet lines are known as:

(1)High side pressure

(2)Discharge pressure

(3)Head pressure

The compressor absorbs vapor refrigerant from the suction line and compresses that

heat to high superheat vapor. As the refrigerant flows across the compressor, it also

removes heat of compression, motor winding heat, mechanical friction, and other heat

absorbs in the suction line. The air conditioner units compressor produce the pressure

different, it’s the air conditioner compressors that cause the refrigerant to flow in a

cycle.

A gas compressor is a mechanical device that increases the pressure of a gas by

reducing its volume. Compressors are similar to pumps: both increase the pressure on

a fluid and both can transport the fluid through a pipe. As gases are compressible, the

compressor also reduces the volume of a gas. Liquids are relatively incompressible,

while some can be compressed, the main action of a pump is to pressurize and

transport liquids.

(2) The condenser:-

In this refrigeration cycle diagram, the air conditioner condenser is air cooled

condenser. It functions the same way as the evaporator but it does the opposite. The

condenser units are located outdoor with the compressor. It purposes is to reject both

sensible and latent heat of vapor absorb by the air conditioner units.

46 ITM/EE/2010/062

The condenser receives high pressure and high temperature superheats vapor from the

compressor and rejects that heat to the low temperature air. After rejected all the

vapor heat, it turns back to liquid refrigerant.

The condenser has three important steps:

(1)It’s remove sensible heat or (de-superheat)

(2)Remove latent heat or (condense)

(3)Remove more sensible heat or (sub cooled).

5.6 Desired property of refrigerant:-

There are many desired properties of refrigerant as under below-

(1) Specific heat High

(2) Thermal conductivity High

(3) Latent heat High

(4) Specific volume Low

(5) Viscosity Low

(6) Boiling point Low

(7) Freezing point Low

(8) It should be non toxic.

(9) It should be non inflammable.

(10) It should be non explosive.

(11) It should be non pollutant.

(12) It should be non corrosive.

47 ITM/EE/2010/062

(13) It should be non irritating.

(14) It should be colourless and odorless.

(15) It should be mix with mineral oil.

(16) It should be electrically insulated.

(17) Easy leak detection.

(18) Chemically stable.

(19) Cost effective.

(20) Easily available.

5.7 Refrigerant:-

In the older days R-12 refrigerant are used but in present R-134 refrigerant is used in

ac. The main reason behind it is R-12 is compatible with mineral oil, while R-134 is

compatible with synthetic oil. It is not much harmful to ozone layer and safe

according to globle warming.

5.8 PRECOOLING RECTIFIRE

5.8.1 General:-

The pre cooling rectifier is principally used for precooling the air conditioned

coaches, before placing them along with other coaches on the platform lines for

entraining. These rectifiers are also used to charge the high capacity 110 volts lead

acid batteries forming part of the equipment/accessories of the air conditioned

coaches. They essentially derive their supply from the three phases L.T. mains in the

railways yards where they are stable maintenance checks. They also come in handy

when the coaches are to stop for long periods in stations platforms to avoid drain on

the batteries. 48 ITM/EE/2010/062

5.8.2 Construction:-

The precooling rectifier is split in to transformer box and diode cubicle. The

transformer box is mainly up of two parts. The top half forms the main frame work

made up of sheet iron construction on angle iron frame work in which the transformer

together with control and protection arrangement is hung from the rigid structure at

the top frame. The bottom half, also of sheet iron construction on angle iron frame

work forms a flood proof tray and covers the bottom portion of the transformer. The

top and bottom parts of the transformer box are bolted together by set of bolts spread

all around with gasket to prevent entry of water and moisture.

Two numbers of hinged doors with locking arrangement are provided on the

transformer box. The bigger door provides access to the input/output connections and

the HRC fuses. This door has an acrylic window to facilitate viewing of the dc

ammeter and the unit ‘ON’ lamp indication. The small door provides access to the tap

changer switches S1 & S2 and the switch on push button switch S3. This portion is

segregated from the live parts by a metal shield to avoid inadvertent contact with the

live parts while operating the switches.

The diode cubicle box is also of sheet iron construction on rigid angle iron frame

work. A single hinged door with locking arrangement provides access to the

input/output connections and the dc output HRC fuses. Suitable cable entry holes

have been provided for the incoming and outgoing cable connections.

5.8.3 Operation:-

The general principal of steeping down the input 3 phase ac supply and rectifying it to

dc through a full wave bridge rectifier has been followed.

The transformer has been specially designed to suit the space constraint generally

encountered by under slung equipment without sacrificing the performance. The input

49 ITM/EE/2010/062

3 phase ac supply is brought on to three terminal studs and through HRC fuses F1,F2

& F3, the tap changer switches S1 & S2, conductor K and thermal overload relay

‘OL’ is fed to the primary of the transformer in delta configuration. The switch S1

controls four taps of fine adjustment on the primary winding. The combined selection

of taps provides the required output dc current.

The secondary winding is in ‘star’ configuration. The output of the secondary,

brought on copper flat terminals pads, is fed through external cabling to the input

copper flat terminal pads in the diodes cubicle. The six nos. of diodes (three nos. body

of cathode type and three nose body of anode type) in bridge configuration rectifier

the ac in to dc and the dc output is brought on to two terminal bolts through copper

bus bars and HRC fuses.

Since the unit is designed for the slandered 200 amps output and 35% overload for a

very short duration of about 10 seconds, the dc ammeter sensing the current through

the current through the shunt provided on the diode cubicle is fitted on to the

transformer box itself with a red band over the range between 200 and 300 amps. The

availability of the ammeter on the transformer itself enables the selection of tap

according to requirement of dc current. A shunt in the negative bus provides means to

measure the dc output current.

5.8.4 Protection & Indication:-

A thermal overload relay ‘OL’ in conjunction with the contactor ‘K’ protects the

transformer against sustained overloads. HRC fuses F9 and F10 have also been

provided in the dc output side. Besides, HRC fuses F6 and F7 are provided on the

control circuit. HRC fuses F4 and F5 are provided for the two terminals brought on

from the two phases of the input voltage or other purpose. HRC fuses F8 has been

provided in the indication lamp circuit.

The unit can be switched on by the push button switch S3 which energies the coil of

contactor K. The switch S3 is interlocked with switches S1 and S2 such that the

50 ITM/EE/2010/062

transformer can be switched ‘ON’ only if the switch position is at No.1 in both S1 and

S2. This is necessitated assuming that the input voltage is high and the transformer is

to be energized with lowest selectable output. Once the unit is switched ON, the

desired output can be obtained by selecting the taps. Facility has been given to

electrically interlock the push button switch further with the pre cooling plug in the air

conditioned coach so that any attempt to withdraw the pre cooling plug while the unit

is ON would trip the unit. This is achieved by using terminals P1 and Q1 brought out

on the SMC board.

However, it may not be possible to open the door, if the air conditioned coach stops at

platforms with transformer box in the platform wall side. In such cases, the interlock

between S1 and S2 should be over ridden and hence a terminal no.11 brought out to

the coach will enable switching ON of the transformer and rectifier irrespective of the

position of switches S1 & S2.

In the ‘ON’ load tap changer rotary switched S1 & S2, provision has been made in the

switch itself so that the movement of switch position from 4 to 1 or vice versa is

blocked. This is necessary as the case may be which can be harmful. An ammeter of

range 0-300A (operating from 300 amps 75 mille volts shunt) is housed in the

transformer box. Also a lamp connected across two of the phases of the secondary

indicates the ON condition of The unit. A capacitor network in the diode cubicle

serves as a surge suppressor.

5.8.5 Technical Specification:-

Input voltage : 415 volts 3 phase ac 50 Hz.

Output voltage : 135 volts dc nominal

Output current : 200 amps dc nominal

Transformer configuration : delta-star with taps on primary

Class of insulation : class ‘F’

Diodes : 300 amps/1000 volts

51 ITM/EE/2010/062

Type of cooling : naturally air cooled

Efficiency : 90%

Dimension : transformer box = 110 X 545 X 620 MMM

: Diode cubicle = 1100 X 505 X 600 MMM

COMPONENTS LIST:-

S.NO. CIRCUIT DESCRIPTION CAPACITY

RATTING

UNIT

1 F1,F2,F3 HRC Fuse Mains 63 Amps 3

2 F4-F8 HRC Fuse Control 2 Amps 5

3 F9,F10 HRC Fuse Output 250 Amps 2

4 K Contactor 63 Amps, 1

5 O Thermal Overload Relay 40 Amps 1

6 S1,S2 4 Pole 4 Way Rotary Switch 63 Amps 2

7 S3 Push-button Switches 5 Amps/500V 1

8 A Ammeter DC 0-300A/75mV 1

9 TX Transformer 415/44V 1

10 L Indication lamp holder Filament lamp 7W/250V 1

11 D1-D3 Diode body anode 300A/1000V 3

12 D4-D6 Diode body cathode 300A/1000V 3

13 SH Shunt 300A/75mV 1

14 D7-D15 Surge arrestor Capacitor 2MicroF/440V 9

52 ITM/EE/2010/062

Table 5.1:- Precolling rectifier component list

CONCLUSION

During my 30 days practical training at north western railway, Ajmer I got

information and experience from my relevant section. I visited following section.

1. Railway Power House

2. Electrical Repair Shop

3. Carriage and Wagon Shop

In railway power house of the north western railway, I learnt about the distribution of

electrical power to the different unit of the plant like carriage workshop, loco

workshop, EPR section etc. I also learnt about the circuit breaker, various protective

relay, capacitor bank for power factor improvement I also studied the Diesel generator

set of 1750 KW ,500 KW ,which are used in case of power supply failure from

R.S.E.B.

In electrical repair and maintenance of electrical shop, I learnt about the maintenance

of electrical motor like single phase and three phase of different type like squirrel

cage induction motor and slip ring induction motors, dc motor of various rating and

also about the rewinding of motor, about various material used for winding, how to

check for any fault etc.

In carriage and wagon shop I learnt about the train lightening system, alternator

section ,ERRU unit and battery section. I learnt about the maintenance of battery and

alternator .

I am really thankful to MR. Manish Goyal (DY. CEE.)

It was definitely a knowledgeable experience taking training in Ajmer. It is indeed a

vast industry with lot much to offer us as students of P and

53 ITM/EE/2010/062

No doubt it showed that mere theoretical and bookish knowledge need to be

supplemented with a able practice knowledge. And this very practical knowledge was

given very ably by the personals of Railway.

Every one at Railway ranging from the workers at stop to supreme head gave their

able support to us. They explained each and everything in best way to make us

understand the complete working of vast industry such as RAILWAY. They all were

very Co-operative.

Railway has helped us in gaining practical knowledge mentioned above to great

extent. The staff of railway is very supportive and helpful. They gave their best and in

such a easy way in which we can understand. They told us very valuable things which

are bard to learn merely from books.

For once again I would like to thank from the core of my heart, to everybody who

helped me and cooperated with me for my successful training.

54 ITM/EE/2010/062