Summer Training Report

Electric Locomotive Shed

Gomoh Dhanbad

Summer Training Report

10th June to 9th July 2015

Guided By - Submitted By- Mr. Vinay Sir SUNIL KUMAR

ACKNOWLEDGEMENT

I am thankful to the organization"ELECTRICAL LOCO SHED

GOMOH DHANBAD" for providing necessary facility to carry out my training successfully. It is our duty to record our sincere thanks and gratitude towards the institute staff, who helped us in bringing this project to its present form. The valuableguidance and interest taken by them has been a motivator and source ofinspiration for me to carry out the necessary proceedings for the project to becompleted successfully. Also, we are highly obliged to the head of our training and placement cell who provided us such a great opportunity to do our summer training in a reputed institute like "ELECTRIC LOCOMOTIVE SHED DHANBAD".

CONTENTS

1- About the company

2- Introduction

3- Operation of Locomotive

4- Different Equipment In Electric

Locomotive 5- Dc Motor Brush Holder

6- Performance Of Carbon Brushes and

Failure of carbon brushes

7- Installation of Carbon Brushes

8- Causes of failure of Commutation

9- Main Cause of Brush Failure

10- Conclusion

About The Company

The Electric loco shed, Gomoh, Dhanbad

was established during the year 1965 for homing 11 locomotives.

This shed was commissioned primarily to meet the requirement of

passenger and goods traffic over Indian railways. At present the

shed has been expended suitably to home 176 loco motives for

hauling, passenger and goods traffic.

The shed is responsible for carrying out monthly inspection

schedule viz. IA, IB, IC, I0& ICO in addition to annual and

intermediate overhauling schedules.

Further the unscheduled repairs to electric locos of CNB shed &

other sheds are being done as per requirements of RDSO organizati

on & HQ’s instructions. All modification&specialmaintenance

instructions, approved by RDSO & N.Rly. Hd. Qtr. are also carried

out as per the guide lines being issued from time to time.

ELECTRIC LOCO MAINTENANCE SHED

Electric Loco Shed maintains locomotive for utilization in freight

and passenger train. All the miner and major inspection are carried

out in the shed on a regular schedule specified by RDSO (Research

Design Standard Organization). Monthly schedule are done at an

interval of 45 days and major schedule are carried out after 18

months.

OPERATION OF LOCOMOTIVE

The electric locomotive basically works at 25 KV, 50Hz supply. The

25KV AC supply is drawn from overhead catenaries wires. The

supply from overhead wires are drawn through a pantograph

inside the loco transformer. This transformer is an

autotransformer from which regulated voltage is taken to a

rectifier block for conversion from AC to DC .It may be worth

mentioning that the final tractive effort is through DC traction

motor hence AC is required to be converted to DC. The DC current

from rectifier block is then filtered to pure DC and then fed to

traction motor.

There are 6 traction motors which works parallel to provide the

attractive effort for hauling the train.

All the operations are controlled through control circuit which

works at 110 volt DC. Various power equipments during operation

gets heated up and hence to cool the same, it is done by various

blowers.

Different Equipments in an Electrical

Locomotive

1) Pantograph

It is pneumatically operated equipment mounted on the roof

for collection of current from overhead wire.

2) Main Transformer

It is an autotransformer which is utilized for drawing various

grades of voltage required for operation of locomotive.

3) Rectifier

This unit consists of rectifier diodes connected in bridge for

conversion of AC current to DC current.

4) Traction Motor

The traction motor is one of the most important equipment

in the locomotive which transmits power to wheels for

moving the trains.

5) Auxiliary Circuit

This Circuit is three phase 415 volts which supplies current to

various three phase induction motors used for driving

blowers for forced air cooling of major equipments like

transformer, rectifier, smoothing reactor and traction motor.

This 3 phase line voltage is supplied by either static converter

or Rotary ARNO Converter.

6) ARNO Converter

Arno converter , is specific-duty machine for conversion of a

single-phase supply into a three-phase supply. While the

electric traction supply is standardized as single-phase A.C.

supply, a three-phase supply is needed on locomotives for

driving certain auxiliary equipments. The function of the Arno

converter is to convert the incoming single-phase supply in to

a three-phase supply for the auxiliaries.

ARNO Converter is of vertical construction and has a flexible

mounting .The machine is of robust mechanical construction

to withstand the several vibrations encountered on

locomotives.

TECHNICAL DATA

Single-phase input Three-phase output

KVA 150 KVA 120

Volts 380 Volts 380

Amps 395 Amps 190

Frame VA-330

Class ’F’

Connection: Star RPM 1490 Cycle 50

OPERATIONAL PRINCIPLE

The single-phase supply of 380 volts AC is fed ‘direct’ to the

‘U’ & ‘V’ phases of the Arno converter. Since the ARNO

Converter is connected to single-phase supply, no starting

torque is developed. For starting the ‘ARNO’ split phase

starting method has been employed. The W phase winding is

connected to the supply phase U through a starting resistor

R-118 and starting contactor C-118 for a short duration to

start the Arno. Thus unbalanced three-phase voltage is

impressed to each phase winding of Arno converter and the

starting torque is developed .the Arno Converter picks up

speed within five seconds. After the Arno has gained

sufficient speed, the phase W is opened from the starting

circuit by starting contactor C-118.

The Arno converts the single phase input into 3 phase output

as 380 volt ± 22.5%. The three-phase output of the Arno

converter is connected to the auxiliary motors.

7) Control Circuit

The control circuit is purely 110 volt DC and the most

important network for handling various operational feature

of the locomotive. All the power equipment and auxiliary

circuit equipment are controlled through various switches in

110 volt circuit provided in the driving cab. All the circuit and

equipment in the high voltage power side & auxiliary circuit

equipment and the control circuit is protected against

overloading, short circuiting and earth fault. For this purpose

various relays have been used as protection device so as to

protect the circuit from any mal functioning.

8) Asynchronous Motor

Modern traction motor type using three phase AC electrical

supply and now the favoured design for modern train

traction systems. Can be used on DC and AC electrified

railways with suitable control electronics and on diesel-

electric locomotives.

9) Axle Brush

The means by which the power supply circuit is completed

with the substation once power has been drawn on the

locomotive. Current collected from the overhead line or third

rail is returned via the axle brush and one of the running rails.

10) Battery

All trains are provided with a battery to provide start up

current and for supplying essential circuits, such as

emergency lighting, when the line supply fails. The battery is

usually connected across the DC control supply circuit.

12) Camshaft

Most DC electric traction power circuits use a camshaft to

open or close the contactors controlling the resistances of

the traction motor power circuit. The camshaft is driven by

an electric motor or pneumatic cylinder. The cams on the

shaft are arranged to ensure that the contactors open and

close in the correct sequence. It is controlled by commands

from the driver's cab and regulated by the fall of current in

the motor circuit as each section of resistance is cut out in

steps. The sound of this camshaft stepping can be heard

under many older (pre electronics) trains as they accelerates.

14) Chopper Control

A development in electric traction control which eliminates the

need for power resistors by causing the voltage to the traction

motors to be switched on and off (chopped) very rapidly during

acceleration. It is accomplished by the use of thyristors and will

give up to 20% improvement in efficiency over conventional

resistance control.

15) Circuit Breaker

An electric train is almost always provided with some sort of

circuit breaker to isolate the power supply when there is a fault,

or for maintenance. On AC systems they are usually on the roof

near the pantograph. There are of two types - the air blast circuit

breaker and the vacuum circuit breaker or VCB. The air or vacuum

part is used to extinguish the arc which occurs as the two tips of

the circuit breaker are opened. The VCB is popular in the UK and

the air blast circuit breaker is more often seen on the continent of

Europe.

16) Contactor

Similar to a relay in that it is a remotely operated switch used to

control a higher power local circuit. The difference is that

contactors normally latch or lock closed and have to be opened by

a separate action. A lighting contactor will have two, low voltage

operating coils, one to "set" the contactor closed to switch on the

lights; the other to "trip" off the lights.

17) Converter

Generic term for any solid state electronic system for converting

alternating current to direct current or vice versa. Where an AC

supply has to be converted to DC it is called a rectifier and where

DC is converted to AC it is called an inverter. The word originated

in the US but is now common elsewhere.

18) Cooling Fans

To keep the thyristors and other electronic power systems cool,

the interior of a modern locomotive is equipped with an air

management system, electronically controlled to keep all systems

operating at the correct temperature. The fans are powered by an

auxiliary inverter producing 3-phase AC at about 400 volts.

19) Creep Control

A form of electronically monitored acceleration control used very

effectively on some modern drive systems which permits a certain

degree of wheel slip to develop under maximum power

application. The GM Class 59 diesel-electric locomotive built for

the UK has this system. A locomotive can develop maximum slow

speed tractive effort if its wheels are turning between 5% and

15% faster than actually required by the train speed.

21) Dynamic Braking

A train braking system using the traction motors of the power

vehicle(s) to act as generators which provide the braking effort.

The power generated during braking is dissipated either as heat

through on-board resistors (rheostatic braking) or by return to the

traction supply line (regenerative braking). Most regenerative

systems include on board resistors to allow rheostatic braking if

the traction supply system is not receptive.

The choice is automatically selected by the traction control

system. .

22) Grid

Train or locomotive mounted expanded steel resistor used to

absorb excess electrical energy during motor or braking power

control. Often seen on the roofs of diesel electric locomotives

where they are used to dissipate heat during dynamic braking.

23) Ground Relay

An electrical relay provided in diesel and electric traction systems

to protect the equipment against damage from earths and so-

called "grounds".

The result of such a relay operating is usually a shut-down of the

electrical drive. Also sometimes called an Earth Fault Relay.

Electrical Connections

The primary function of the brush involves conducting current. In

many cases the brush holder is also a part of this electrical circuit.

Therefore it is necessary that all electrical connections are of

minimal resistance to provide the best path for current flow from

the main lead connection to the contact surface. Corrosion,

contamination, or electrolytic action over a period of time can

cause dramatic increases in resistance which then requires

cleaning. Careless installation of the brushes or the holders can

lead to loose connections. Any high resistance in the brush circuit

will result in excess heat or an undesirable path of current flow and

unequal loading of the brushes.

On fractional horsepower cartridge style brushholders with captive

coil spring type brushes the current should flow from the clip

connector at the bottom of the holder up the brass insert to the cap

on the end of the brush and then down through the shunt to the

carbon. The brushes fail very quickly if the round or eared cap on

the end of the brush does not make proper contact with the brass

holder insert. When this condition exists current will flow directly

from the brass insert to the spring or to the carbon. In either case

there will be extreme heat, loss of brush contact, commutator wear,

and eventually motor failure.

Another problem with larger frame sizes can occur when the

holder mounting is part of the electric circuit. If the holder

mounting surface becomes dirty, corroded, or even painted over

then current will again need to follow another path and thereby

cause problems.

Return to top of page.

Summary

The general knowledge and experience in the field on rotating

equipment has been slowly declining for many years. In addition

brushholders have seldom ever received proper attention during

trouble shooting or as part of a maintenance program. Therefore it

is hoped that the above information will be helpful in creating

awareness of the potential problems with brushholders as a very

critical component in the satisfactory performance of carbon

brushes on motors, generators, and other types of sliding contacts.

The important factors to check for proper functioning of the holder

and brush are:

1. Inside holder dimensions

2. Holder spacing

3.Holder angle

4.Holder height

5.Spring force

6. Electrical connections

When there is an opportunity to implement new holders, the use of

the principles mentioned above along with the coordination of the

latest constant pressure holder .

Installation Steps

Carbon Brush 1-Disconnect the power to the machine using approvedlock-out procedures. 2. Remove all old brushesfrom the holders. Make Noteof any unusualconditions of the brushesincluding roughness orburning of the contact face, Polished sides on thecarbon, excess heat on thewires, or frayed shunt wires. Unusual brush conditionsare indications of the need for and improved brushdesign or for maintenanceon the machine. 3. Inspect the commutatorfor unusual conditions for high bars and mica.Make note for required maintenance. 4. Check the inside holdercavity for dust, dirt, oil, deposits, carbon buildup,corrosion, or burned areas and clean as needed. 5. Check the terminal connectionarea and clean, asneeded. 6. Brush holders should besecured to their mount andchecked that none havebecome loosened or are outof alignment. 7. Measure spring forces to ensure there is consistentcontact force at therecommended level. Usethe measured force to calculate the spring pressurefor comparison withrecommended level of 4.0+PSI. 8. Remove the old film fromthe brush tracks, if the newbrushes are made from a different grade. Dry untreatedcanvas applied witha pressure block or a rubberabrasive. Seater stone canbe used as an alternative. However, the remainingdust must be vacuumed or blown out of the machine.

9. Install new brushes in allholders with attention to theorientation on angled designs.Ensure that the brushes can move freely inthe radial direction and thatthere is a relatively close fitin the tangential and axialdirections. 10. Apply the pressure springto the top of the brush. 11. Pull up on the brush andallow to gently return tocontact with the commutatoror ring to ensure there is no binding of thebrush and spring. 12. Connect the terminals. Besure all terminal connections are tight and secure. 13. Seat the brushes to the contour of the commutatorusing non-metal bearingsandpaper or garnet paper.Do NOT use emery. Mediumcoarse grade paper pulledunder the brush face in thedirection of rotation improvesthe quality of the brush contact surface andspeeds the process. Thereshould be at least 90% ofthe brush face seated to the contour of the contactsur face prior to operating the machine at load. Oncethis level has been achieved, then the resultingdust in the machine aroundthe brushes, holders, andcommutator should bevacuumed or blown out. 14. Operate the machine at noload for the final wear-incontour of the contact surfaces in order to ensurecomplete electrical contactof the brushes. This procedureallows the brush tomake intimate contact in itsoperating position in theholder. 15. The machine is ready foruse. The film process onthe contact sur face can beenhanced with the use of anuntreated hardwood burnishingblock or a rubber polishingstone. This procedurecan reduce the high frictionand brush dust developed during the initial filmforming period. NOTE: In some cases timeallotment, operating conditions, or performance issues mayrequire the replacement of lessthan a full set of brusheswithout normal seating. Then, it is especially important to

adhere to step 11 with extendedoperation at no-load. Shortcuts on procedures forbrush installation will result inexcess electrical damage to thebrush face and the contact surface. Causes of Commutation Failure

1- Streaking

2- Threading

3- Bar Edge Burning

4- Grooving

5- Slot Bar Marking

6- Photographing

7- Copper

Streaking

Causes • Low or unequal springpressure • Low current loads • Contaminated atmosphere • High humidity • Copper particle pickup fromcommutator

(streaking)

THREADING

Causes • Low or unequal springpressure • Low current loads • Contaminated atmosphere • High humidity • Uneven current distribution • Conditions have beenmaintained for a long period of time and causedcommutator damage

BAR EDGE BURNING

Causes • Low or unequal springpressure • Incorrect brush alignment /off neutral

• Wrong brush grade • Sparking caused bycommutation problems • Incorrect interpole strength

Grooving

Causes • Low or unequal springpressure • Contaminated atmosphere • Low humidity andtemperature • Abrasive brush grade

SLOT BAR MARKING

Causes • Low or unequal springpressure • Excess vibration • Wrong brush grade • Commutator becomesoverheated and softened • High Friction

Copper Drag Causes • Uneven current distributionin armature windings • Unequal number of windingsin adjacent slots • Inconsistency in armaturewindings related to numberof coils, slots, andcommutator bars.

Carbon Brush Failure The most common cause of carbon brush failure is incorrect spring tension. Oncethe proper force is applied, grade selection can be fine-tuned to ensure optimumbrush and machine performance. For reference, the chart below indicates the recommended ranges of spring pressure for various applications and the methodof calculating spring pressure from the measured spring force. Spring Pressure Industrial D.C Applications 4-6 psi 280-420 g/cm2 WRIM & Sync. Rings 3.5-4.5 psi 240-310 g/cm2 High Speed Turbine Rings Soft Graphite Grades 2.5-3.5 psi 170-240 g/cm2 Metal Graphite Brushes 4.5-5.5 psi 310-390 g/cm2 FHP Brushes 4-7 psi 280-490 g/cm2 Traction Brushes 5-8 psi 350-560 g/cm2 For brushes with top and bottom angles greater than 25 degrees, add an extra .5-1 psi = 35-70 g/cm2 Spring (P.S.I.) =Measured Force (lbs.) Pressure Brush Thickness (in.) X BrushWidth (in.) CONCLUSION

A locomotive is a railwayvehicle that provides the motive power for a train. The

word originates from the Latinloco – "from a place", ablative of locus, "place" +

Medieval Latin motivus, "causing motion", and is a shortened form of the term

locomotive engine,[1] first used in the early 19th century to distinguish between

mobile and stationary steam engines.

A locomotive has no payload capacity of its own, and its sole purpose is to move

the train along the tracks. In contrast, some trains have self-propelled payload-

carrying vehicles. These are not normally considered locomotives, and may be

referred to as multiple units, motor coaches or railcars. The use of these self-

propelled vehicles is increasingly common for passenger trains, but rare for freight.

Vehicles which provide motive power to haul an unpowered train, but are not

generally considered locomotives because they have payload space or are rarely

detached from their trains, are known as power cars.

Traditionally, locomotives pull trains from the front. Increasingly common is push-

pull operation, where a locomotive pulls the train in one direction and pushes it in

the other, and can be controlled from a control cab at the other end of the train.

Like great books, no project is created entirely by an individual. There are many people involved in this project too and have helped a lot right from the beginning till the completion of our project. Any bouquets for the merits in this project should go to our door. Any brickbats we are ready to catch ourselves. It is with a great sincerity, we convey our heartfull gratitude to our Mr.Mohammad Israr, Supervisor, Electric Loco Shed, Kanpur, for his excellent guidance, valuable advice and ample co-operation throughout the training. It is a proud privilege to have availed of the opportunity of guidance.