CHAPTER 1

1. INTRODUCTION

An electric locomotive is a locomotive powered by electricity from an external source.

Sources include overhead lines, third rail, or an on-board electricity storage device such

as a battery, flywheel system, or fuel cell.

One advantage of electrification is the lack of pollution from the locomotives

themselves. Electrification also results in higher performance, lower maintenance costs,

and lower energy costs for electric locomotive.

Power plants, even if they burn fossil fuels, are far cleaner than mobile sources

such as locomotive engines. Also the power for electric locomotives can come from

clean and/or renewable sources, including geothermal power, hydroelectric power,

nuclear power, solar power, and wind turbines. Electric locomotives are also quiet

compared to diesel locomotives since there is no engine and exhaust noise and less

mechanical noise. The lack of reciprocating parts means that electric locomotives are

easier on track, reducing track maintenance.

Power plant capacity is far greater than what any individual locomotive uses, so

electric locomotives can have a higher power output than diesel locomotives and they

can produce even higher short-term surge power for fast acceleration. Electric

locomotives are ideal for commuter rail service with frequent stops. They are used on

high-speed lines, such as ICE in Germany, Acela in the US, Shinkansen in Japan and

TGV in France. Electric locomotives are also used on freight routes that have a

consistently high traffic volume, or in areas with advanced rail networks.

Electric locomotives benefit from the high efficiency of electric motors, often

above 90%. Additional efficiency can be gained from regenerative braking, which allows

kinetic energy to be recovered during braking to put some power back on the line. Newer

electric locomotives use AC motor inverter drive systems that provide for regenerative

braking.

1

CHAPTER 2

2. LOCATION

Mughalsarai city and a municipal board in Chandauli district in the Indian state of Uttar

Pradesh. Located around 10 kilometres (6.2 mi) from Varanasi, it is an important railway

junction of the Indian Railways. Once, it enjoyed the position of the largest railway

arshalling yard of Asia. The Grand Chord section, which starts from Asansol, West

Bengal, terminates at Mughalsarai. Mughalsarai is most famous for its railway yard and

its railway colonies. There are about 16 railway colonies. The Mughalsarai Railway

Division belongs to East Central Railway (ECR) Zone of the Indian Railway. There is

large electric traction workshop in Mughalsarai, which is situated 5km away from

mughalsarai junction. The workshop has an area of 2.1 sq.km .Here in electric traction

workshop, the loco parts is repaired, which is manufactured in Chittaranjan Locomotive

Works (CLW).

There are four major OHE depots e.g. Mughalsarai, Dehri-on-Sone, Gaya on G.C

section and Japla in B.D. section. In addition there are four OHE Sub-depot e.g.

Karmanasa, Kudra,Sonnagar and Rafiganj. All OHE major depots/Sub-depots are

equipped with one tower wagon and staff. Road vehicles are also provided with major

depots except JPL. There is one divisional store and central workshop for repair and

maintenance including automobile section under Sr. Section Engineer (S&W). Traction

Power Control organisation functions under CTPC and RCC under a separate Section

Engineer (R.C.) at Mughalsarai. Remote Control Centre at Mughalsarai has been

provided with PC based SCADA system of NELCO make under AMC to OEM. MGS

Div. has 3 nos. of Rly owned TSS at RFJ,KTQ&JPL and power is purchase at 132 KV

AC RTS-II . MGS also has 33 KM of 2x132 KV transmission line from SEB to JPL

fully owned and maintained by Rly. There are 03 nos. of Grid Sub-Stations at

Karmanasa, Sonnagar & Gaya. These Grid Sub-stations are owned, maintained and

operated by Bihar State Electricity Board. Power is purchased at 25 kV AC.

2

CHAPTER 3

3.1 General Description of Locomotives.

1. AC lomotive type WAP- 4 are manufactured in CLW based on RDSO

specification no c wam006 OF OCTOBAR 1978 locomotives are design to haul

passenger trains.

2. WAP-4 class locomotive are design for operation on 25kv are single phase 50hz

overhead line locomotive is of CO-CO type consisting of single body on two

bogies is equipped with 3 axle hang nose suspend traction motor. To drive the

axle through pinion and gear and the body has driving at either end.

Interconnection between cabs is provided by two corridors on either side.

3. Current is controlled from overhead line by pantograph and is fed to an auto

transformer through a vacuum circuit breaker mounted on the roof. The

transformer step-down voltage from 25kv to 2* 1000v. It is then converted to dc

trough the bridge controlled SCRs and fed to the traction motors speed regulation

is obtained by varying the voltage at motor terminals by tap changers.

Traction motors are permanently connected in 6p combination. Locomotive is

provided with air brakes.

4. The auxiliary machines are fed from arno converter which convert the incoming

ac signal phase supply to 3- phase supply at 45% if one rectifier with half power.

3.2 General Characteristic of Locomotives.

Description of equipment used on locomotive

Power equipment

Pantograph

Circuit breaker

Vacuum CB (conventional)

Air blast CB (high speed)

Current 600A/1000A 400

Voltage 25kv Ac 25Ac

Pressure 11kg/cm2 10kg

Opening time ≤60m/sec.

Rupturing capacity 400MVA

3

1. Main transformer

Phase single

Cooling OFAF

Primary voltage 25kv(normal)

Voltage at 32 tapped 2*1000v

Under catenary voltage 22.5kv

Primary i/p 5670KVA

Secondry o/p 5400KVA

Auxiliary ckt. 270KVA

No. Of taps 32

2. Tap changer

Rated voltage 25kv

Rated current 400A

Frequency 50hz

Frequency fluctuation 48.5-51.5hz

No. Of taps 32

Methods of drive Electro-pneumatically operate

servo motor

3. SCR

No. Of cubic per loco 2

Rated current 3300A

Max.starting curret 4050A

Connection bridge

No. Of diodes 4 per bridge

4. Traction motor

Type HS 15250A

continuous o/p 630kv

volts 750v

starting current 1350A

current continuous 900A

speed 895Rev/min.

max. Service speed 2150Rev/min.

4

CHAPTER 4

4.1 Traction Motor

CLW During this financial year, CLW has so far produced 715 traction motors, setting

another production record for In the corresponding period of the previous financial year,

CLW produced 316 motors only, indicating an improvement of 126 per cent year on

year (YoY). CLW had decided to sharply raise the manufacturing of three-phase traction

motors. The unit had produced 156 traction motors till January 2006, setting another

cumulative production record in the history of CLW The previous best ever for

production at CLW was 132 traction motors in 12 months of the financial year 2003-

2004 For the first time, 55 Hitachi traction motors were dispatched as spared to

Railways for use in general maintenance in January 2006.

4.2 Types of traction motor.

1. 3 phase traction motor

2. Hitachi traction motor

3 phase Traction motor refers to electric motor providing the primary rotational torque

of a machine, usually for conversion into linear motion (traction).Traction motors are

used in electrically powered rail vehicles such as electric multiple units and electric

locomotives, As the DC motor starts to turn, the interaction of the magnetic fields inside

causes it to generate a voltage internally. This back EMF (electromagnetic force)

opposes the applied voltage and the current that flows is governed by the difference

between the two. As the motor speeds up, the internally generated voltage rises, the

resultant EMF falls, less current passes through the motor and the torque drops.

The motor naturally stops accelerating when the drag of the train matches the torque

produced by the motors. To continue accelerating the train, series resistors are switched

out step by step, each step increasing the effective voltage and thus the current and

torque for a little bit longer until the motor catches up. This can be heard and felt in

older DC trains as a series of clunks under the floor, each accompanied by a motor are

strong, producing high torque (turning force), so it is ideal for starting a train. The

disadvantage is that the current flowing into the motor has to be limited, otherwise the

supply could be overloaded or the motor and its cabling could be damaged. At best, the

5

torque would exceed the adhesion and the driving wheels would slip. Traditionally,

resistors were used to limit the initial current.

Fig. 4.1 3-Phase traction motor

2.HITACHI TRACTION MOTOR TYPE HS15250A

Hitachi traction Motor is one of the most critical and vital equipment in conventional

Electric locomotives type WAP-7 & WAP-4 under production at CLW. The production

of Hitachi TM is now completely stabilized.

6

Fig. 4.2 HITACHI TRACTION MOTOR

4.3 Transportation applications

Before the mid-20th century, a single large motor was often used to drive multiple

wheels rough connecting rods that were very similar to those used on steam locomotives.

Examples are the Pennsylvania Railroad DD1, FF1 and L5 and the various Swiss

Crocodiles. It is now standard practice to provide one traction motor driving each axle

through a gear drive. Usually, the traction motor is three-point suspended between the

bogie frame and the driven axle; this is referred to as a "nose-suspended traction motor".

The problem with such an arrangement is that a portion of the motor's weight is

unsprung, increasing unwanted forces on the track. In the case of the famous

Pennsylvania.

Railroad GG1, two bogie-mounted motors drove each axle through a quill drive. The

"Bi-Polar" electric locomotives built by General Electric for the Milwaukee Road had

direct drive motors. The rotating shaft of the motor was also the axle for the wheels. In

the case of French TGV power cars, a motor mounted to the power car’s frame drives

each axle; a "tripod" drive allows a small amount of flexibility in the drive train allowing

the trucks bogies to pivot. By mounting the relatively heavy traction motor directly to

7

the power car's frame rather than to the bogie, better dynamics are obtained allowing

better high-speed operation.

The DC motor was the mainstay of electric traction drives on both electric and diesel-

electric locomotives, street-cars/trams and diesel electric drilling rigs for many years. It

consists of two parts, a rotating armature and fixed field windings surrounding the

rotating armature mounted around a shaft. The fixed field windings consist of tightly

wound coils of wire fitted inside the motor case.

The armature is another set of coils wound round a central shaft and is connected to the

field windings through "brushes" which are spring-loaded contacts pressing against an

extension of the armature called the commutator. The commutator collects all the

terminations of the armature coils and distributes them in a circular pattern to allow the

correct sequence of current flow. When the armature and the field windings are

connected in series, the whole motor is referred to as "series-wound". A series-wound

DC motor has a low resistance field and armature circuit. Because of this, when voltage

is applied to it, the current is high due to Ohms Law. The advantage of high current is

that the magnetic fields inside.

Electric train, the train driver originally had to control the cutting out of resistance

manually, but by 1914, automatic acceleration was being used. This was achieved by an

accelerating relay (often called a "notching relay") in the motor circuit which monitored

the fall of current as each step of resistance was cut out. All the driver had to do was

select low, medium or full speed (called "shunt", "series" and "parallel" from the way the

motors were connected in the resistance circuit) and the automatic equipment would do

the rest.

4.4 Synchronous AC traction motor

The motor is excited at a frequency proportional to its rotational speed. There is no

collector as on DC motors, which allows a reduction of wear and maintenance costs.

(Note: the synchronous AC traction motor is different from asynchronous AC

(induction) traction motor. Whereas the latter has a simple cage rotor with no power

connections, the synchronous motor has rotor coils fed through slip rings.) In an unusual

arrangement considered to be one of the TGV design's strong points, the traction motors

8

are slung from the vehicle body, instead of being an integral part of the Y230 power

truck (bogie).

This substantially lightens the mass of the truck (each motor weighs 1460 kg), giving it a

critical speed far higher than 300 km/h (186 mph) and exceptional tracking stability. The

traction motors are still located where one would expect them: in between the truck

(bogie) frames, level with the axles, but just suspended differently. Each motor can

develop 1100 kW (when power comes from 25kV overhead) and can spin at a maximum

rate of 4000 rpm.

The output shaft of the motor is connected to the axle gearbox by a tripod transmission,

using sliding cardan (universal-joint) shafts. This allows a full decoupling of the motor

and wheel dynamics; a transverse displacement of 120 mm (5 inches) is admissible. The

final drive is a gear train that rides on the axle itself and transfers power to the wheels.

This final drive assembly is restrained from rotating with the axle by a reaction linkage.

9

CHAPTER 5

5.1 PANTOGRAPH

Pantograph is the device from which locomotive get main supply. It is set up with the

roof of the locomotive.

Fig. 5.1 Pantograph of locomotive

A pantograph (or "pan") is an apparatus mounted on the roof of an electric train or tram

10

to collect power through contact with an overhead catenary wire. Typically a single wire

is used, with the return current running through the track. The term stems from the

resemblance of some styles to the mechanical pantographs used for copying handwriting

and drawings.

A flat slide-pantograph was invented in 1895 at the Baltimore & Ohio Railroad and in

Germany in 1900 by Siemens & Halske. The familiar diamond-shaped roller pantograph

was invented by John Q. Brown of the Key System shops for their commuter trains

which ran between San Francisco and the East Bay section of the San Francisco Bay

Area in California. They appear in photographs of the first day of service, 26 October

1903. For many decades thereafter, the same diamond shape was used by electric-rail

systems around the world and remains in use by some today.

The pantograph was an improvement on the simple trolley pole, which prevailed up to

that time, primarily because the pantograph allows an electric-rail vehicle to travel at

much higher speeds without losing contact with the overhead lines.

The most common type of pantograph today is the so called half-pantograph (sometimes

'Z'-shaped), which has evolved to provide a more compact and responsive single-arm

design at high speeds as trains get faster. The half-pantograph can be seen in use on

everything from very fast trains (such as the TGV) to low-speed urban tram systems.

The design operates with equal efficiency in either direction of motion, as demonstrated

by the Swiss and Austrian railways whose newest high performance locomotives, the Re

460 and Taurus respectively, operate with them set in opposite directions Pantographs

easily adapt to various heights of the overhead wires by partly folding. The tram line

pictured here runs in Vienna.

The electric transmission system for modern electric rail systems consists of an upper

weight carrying wire (known as a catenary) from which is suspended a contact wire. The

pantograph is spring-loaded and pushes a contact shoe up against the contact wire to

draw the electricity needed to run the train. The steel rails on the tracks act as the

electrical return. As the train moves, the contact shoe slides along the wire and can set

up acoustical standing waves in the wires which break the contact and degrade current

collection. This means that on some systems adjacent pantographs are not permitted.

5.2 SUPPLY SYSTEM

11

Pantographs are the successor technology to trolley poles, which were widely used on

early streetcar systems. Trolley poles are still used by trolleybuses, whose freedom of

movement and need for a two-wire circuit makes pantographs impractical, and some

streetcar networks, such as the Toronto Streetcar System, which have frequent turns

sharp enough to require additional freedom of movement in their current collection to

ensure unbroken contact.

Pantographs with overhead wires are now the dominant form of current collection for

modern electric trains because, although more expensive and fragile than a third-rail

system, they allow the use of higher voltages

.

5.3 THREE MAIN STAGES IN THE POWER CIRCUIT 3 PHASE AC

LOCOMOTIVES

5.3.1 Input Converter

This rectifies the AC from the catenary to a specified DC voltage using GTO (gate turn-

off) thyristors. A transformer section steps down the voltage from the 25kV input. It has

filters and circuitry to provide a fairly smooth (ripple-free) and stable DC output, at the

same time attempting to ensure that a good power factor presented to the electric supply.

There may also be additional mechanisms such as transformers, inductors, or capacitor

assemblies to improve the power factor further.

The transformer section is designed with high leakage impedance and other

characteristics, which together with the fine control possible with the GTO switching,

allow the loco to present nearly unity power factor, a very desirable situation from the

point of view of the electricity suppliers (the grid). The main transformer also has some

filter windings which are designed to further attenuate harmonics from the loco's traction

motors which may pass through the filtering in the DC link.

The input converters can be configured to present different power factors (lagging or

leading) to the power supply, as desired. IR's WAP-5 and other 3-phase AC locos are

generally configured to present a unity power factor (UPF). (Note: the power factor

cannot be changed on the run.)

5.3.2 DC Link

12

This is essentially a bank of capacitors and inductors, or active filter circuitry, to further

smooth the DC from the previous stage, and also to trap harmonics generated by the

drive converter and traction motors. Since the traction motors and drive converters

present non-linear loads, they generate reactive power in the form of undesirable

harmonics; the DC link acts as a reservoir for the reactive power so that the OHE supply

itself is not affected.

During regenerative braking this section also has to transfer power back to the input

converter to be fed back to the catenary. The capacitor bank in this section can also

provide a small amount of reserve power in transient situations (e.g., pantograph

bounce) if needed by the traction motors.

5.3.3 Drive Converter

This is basically an inverter which consists of three thyristor-based components that

switch on and off at precise times under the control of a microprocessor (pulse-width

modulation). The three components produce 3 phases of AC (120 degrees out of phase

with one another). Additional circuitry shapes the waveforms so that they are suitable for

feeding to the traction motors.

The microprocessor controller can vary the switching of the thyristors and thereby

produce AC of a wide range of frequencies and voltages and at any phase relationship

with respect to the traction motors. Various kinds of thyristor devices are used to

perform the switching. Currently produced modern locos generally use GTO thyristors

(Gate Turn-Off thyristors), but it is expected that soon insulated-gate bipolar transistors

(IGBTs), which offer extremely high switching speeds allowing for finer control over

the waveforms generated, will be the switching technology of choice.

The WAP-5, WAP-7, WAG-9, andWAG-9H models all use GTOs. At present no Indian

loco uses IGBTs; some trial locos such as the 12X from Adtranz do use this technology,

as do many light-rail and metro locomotives or EMUs around the world. The new AC-

DC EMUs in the Mumbai area (introduced on WR) use IGBTs. The 3-phase AC is fed

to the AC traction motors, which are induction motors. As the voltage and the frequency

can be modified easily, the motors can be driven with fine control over their speed and

torque. By making the slip frequency of the motors negative (i.e., generated AC is

'behind' the rotors of the motors), the motors act as generators and feed energy back to

the OHE — this is how regenerative braking is performed.

13

There are various modes of operation of the motors, including constant torque and

constant power modes, balancing speed mode, etc. depending on whether their input

voltage is changed, or the input frequency, or both.AC motors have numerous

advantages over DC motors. DC motors use commutators which are prone to failure

because of vibration and shock, and which also result in a lot of sparking and corrosion.

Induction AC motors do not use commutators at all. It is hard to use a DC motor for

regenerative braking, and the extra switchgear for this adds to the bulk and complexity

of the loco. AC motors can fairly easily be used to generate power during regenerative

braking. In addition, DC motors tend to draw power from the OHE poorly, with a bad

power factor and injecting a lot of undesirable harmonics into the power system. AC

motors suffer less from these problems, and in addition have the advantage of a simpler

construction.

5.4 Thyristor controlled-rectifier bridge

As the name implies, rectifies the ouput of the main transformer to make 1500V DC.

The thyristors allow a refinement beyond a simple diode bridge: they not only rectify the

current, but can act as a switch and "chop" (turn on and off) the output power. This is

why we speak of a "controlled rectifier". There are two thyristor-diode bridges, one for

each pair of traction motors. From now on in the traction chain, in fact, there are two

separate and independent paths to each of the two power trucks (bogies). This is to

maximize reliability. (under 1500V DC overhead power, all that is used up to here is a

thyristor chopper.) . The development of the thyristor has made possible the use of

frequency controlled AC traction motors and revolutionized traction circuit design. The

thyristor is basically a switch, albeit a very large one, which resembles a common

transistor in the way it works. A thyristor passes current only in one direction, called the

"forward" direction, providing that a suitable voltage is applied to its control electrode,

or "gate". As long as this gate voltage is not present, current cannot flow through the

device.)

14

CHAPTER 6

6.1 TRACTION TRANSFORMER

EMCO manufactures 1-phase and 3-phase Locomotive Transformers upto 7500 kVA, 25

KV class, which is the largest rating being used in India. It's one of the few

manufacturers who have been approved by Indian Railways. Transformers are low

weight and compact in size. EMCO manufactures Traction Power Transformers for the

Indian Railways upto 42 MVA, 220 kV class. These transformers are single phase

double limb wound construction and are specially designed and tested to withstand

frequent.

Locomotive Transformer

Type: Locomotive Transformer

Rating: Upto 7500 kVA for 3-phase locomotives

Voltage: Upto 25 kV Class

Fig. 6.1 AC Traction Transformer 25kv

15

"Electric Trains" redirects here. For the 1995 Squeeze single, see Electric Trains (song).

An electric locomotive is a locomotive powered by electricity from overhead lines, a

third rail or an on-board energy storage device (such as a chemical battery or fuel cell).

Electrically propelled locomotives with on-board fuelled prime movers, such as diesel

engines or gas turbines, are classed as diesel-electric or gas turbine-electric locomotives

because the electric generator/motor combination only serves as a power transmission

system. Electricity is used to eliminate smoke and take advantage of the high efficiency

of electric motors; however, the cost of railway electrification means that usually only

heavily used lines can be electrified. A transformer is a power converter that transfers

electrical energy from one circuit to another through inductively coupled conductors the

transformer's coils.

A varying current in the first or primary winding creates a varying magnetic flux in the

transformer's core and thus a varying magnetic field through the secondary winding.

This varying magnetic field induces a varying electromotive force (EMF), or "voltage",

in the secondary winding. This effect is called inductive coupling. If a load is connected

to the secondary winding, current will flow in this winding, and electrical energy will be

transferred from the primary circuit through the transformer to the load. In an ideal

transformer, the induced voltage in the secondary winding (Vs) is in proportion to the

primary voltage (Vp) and is given by the ratio of the number of turns in the secondary

(Ns) to the number of turns in the primary. Transformers range in size from a thumbnail-

sized coupling transformer hidden inside a stage microphone to huge units weighing

hundreds of tons used in power stations, or to interconnect portions of power grids.

The principle behind the operation of a transformer, electromagnetic induction, was

discovered independently by Michael Faraday and Joseph Henry in 1831. However,

Faraday was the first to publish the results of his experiments and thus receive credit for

the discovery. [2] The relationship between electromotive force (EMF) or "voltage" and

magnetic flux was formalized in an equation now referred to as "Faraday's law of

induction":

6.2 ELECTRIC LOCO TAP-CHANGER

On the Indian Railways, a large number of electric locomotives are in operation today.

Many different models of these locos have been manufactured, many of which have now

been scrapped. However, many of those models which are still in service such as the

WAM-4, WAP-4, WCAM-1, WCAM-2, WCAM-3, WCAG-1, WAG-5, WAG-7, etc.,

use almost the same electrical setup (excepting the newer 3-phase AC locos such as the

16

WAP-5 and WAG-9)..These characteristics are obtained in electric locos on the Indian

Railways by the use of the series-wound DC traction motor which has an inherent

characteristic of exerting a high torque during its starting phase and a high speed during

the running phase when the train resistance is minimal. However in order to have proper

speed control over these traction motors the voltage supplied to these motors must be

varied. Increasing the voltage to the motor increases its torque and speed and vice-versa.

Before explaining the working of the tap-changer provided in these locos, it will better if

the broad outline of the power circuit of these locos is understood properly.

These locos operate on a nominal voltage of 25,000V AC (single phase). The power is

supplied from the overhead equipment (OHE). This power is collected from the OHE by

the pantograph which then passes it to the main circuit breaker (DJ).. This reduces space

requirement and also provides better magnetic coupling. The first transformer is an

autotransformer with around thirty one tapings which are brought out to the tap-changer.

The output voltage of the autotransformer depends on the tap at which the selector of the

tap-changer is resting. Hence, by changing the position of the tap-changer selector the

output voltage of the auto -transformer can be varied conveniently. The Tap-Changer is

provided on the high-tension side of the transformer which reduces its size due to the

lower current. Insulation is enhanced by filling the selector casing with oil. The output of

the autotransformer is fed to the second transformer which has a fixed ratio and steps

down the voltage to a fixed fraction.

The output of this second transformer is then fed to the rectifier blocks (RSI 1 and RST

2). These convert the AC into DC. In turn the DC output is fed into a pair of chokes

known as smoothing reactors (SL 1 and SL 2). The smoothing reactors are provided to

remove the AC ripple which is left over from the rectification cycle. This smoothened

DC is then handed over to the DC switchgear for the line and combination control of the

traction motors and then finally to the traction motors themselves. The subject of this

article is the detailed manner in which the above mentioned tap -changer works. Takes

25kV 50Hz single phase overhead power and converts this to 1500V 50Hz.

17

CHAPTER 7

7.1 BREAKING OF LOCOMOTIVES & ITS TYPES

Breaking is the main function of the locomotives. It is used for holding the locomotives.

Brakes were manually applied and released by turning a large brake wheel located at one

end of each car. The brake wheel pulled on the car's brake rigging and clamped the brake

shoes against the wheels. As considerable force was required to overcome the friction in

the brake rigging, the brakeman used a stout piece of wood called a "club" to assist him

in turning the brake wheel.

The job of a passenger train brakeman wasn't too difficult, as he was not exposed to the

weather and could conveniently move from car to car through the vestibules, which is

where the brake wheel was (and still is, in many cases) located. Also, passenger trains

were not as heavy or lengthy as their freight counterparts, which eased the task of

operating the brakes.

There was nothing to grasp other than the brake wheel itself, and getting to the next car

often required jumping. Needless to say, a freight brakeman's job was extremely

dangerous, and many were maimed or killed in falls from moving trains.

7.2 Types of braking.

1. Regenerative braking

2. Dynamic braking

2.1 Ac dynamic braking

2.2 Dc dynamic braking

1. Regenerative braking

A regenerative brake is an energy recovery mechanism which slows a vehicle or object

down by converting its kinetic energy into another form, which can be either used

immediately or stored until needed. This contrasts with conventional braking systems,

where the excess kinetic energy is converted to heat by friction in the brake linings and

therefore wasted.

The most common form of regenerative brake involves using an electric motor as an

electric generator. In electric railways the generated electricity is fed back into the

supply system, whereas in battery electric and hybrid electric vehicles, the energy is

stored in a battery or bank of capacitors for later use. Energy may also be stored

mechanically via pneumatics, hydraulics or the kinetic energy of a rotating flywheel.

18

During braking, the motor fields are connected across either the main traction generator

(diesel-electric locomotive, hybrid electric vehicle) or the supply (electric locomotive,

electric vehicle) and the motor armatures are connected across braking grids (rheostatic)

or the supply (regenerative). The rolling wheels turn the motor armatures and when the

motor fields are excited, the motors act as generators. Regenerative braking has been in

extensive use on railways for many decades

2. Dynamic braking

Dynamic braking is the use of the electric traction motors of a vehicle as generators

when slowing. It is termed rheostatic if the generated electrical power is dissipated as

heat in brake grid resistors, and regenerative if the power is returned to the supply line.

Dynamic braking lowers the wear of friction-based braking components, and

additionally regeneration reduces energy consumption with dynamic braking, the

electrical energy generated by the motor during braking is directed to a resistor bank

where it is dissipated as heat. A relatively simple control unit is used to connect the

braking resistors when braking is required and modulate the braking current. Because

the braking energy cannot be reused, dynamic braking is used in applications that do not

generate a lot of braking energy or do not have a means for storing braking energy or

using it elsewhere. During dynamic braking the traction motors which are now acting as

generators are connected to the braking grids (large resistors) which put a large load on

the electrical circuit. When a generator circuit is loaded down with resistance it causes

the generators to slow their rotation. By varying the amount of excitation in the traction

motor fields and the amount of resistance imposed on the circuit by the resistor grids, the

traction motors can be slowed down to a virtual stop.

2.1 Ac dynamic braking

Dynamic braking in an AC induction motor is also sometimes called DC injection

braking. You can even get such brakes to put on table saws and the like. What you are

doing is feeding the AC motor with DC current, which is at 0 Hz. Think of the 0 Hz DC

current as shafts and the like.

2.2 Dc dynamic braking

DC voltage is applied to the AC motor windings thus forcing a DC current to flow. The

resulting magnetic field causes an opposing magnetic field to develop in the motor rotor

similar to the action of an eddy-current brake. There is a high braking torque at high

speed and no torque at zero speed. The braking energy is dissipated in the motor rotor.

Since DC braking can be provided by simply altering the switching sequence of the

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VFD, it is very inexpensive. It is used in applications requiring only a small amount of

braking torque. It is often used to reduce the motor speed prior to applying a friction

brake.

7 . 3 A I R B R A K E

In the air brake's simplest form, called the straight air system, compressed air pushes on

a piston in a cylinder. The piston is connected through mechanical linkage to brake

shoes that can rub on the train wheels, using the resulting friction to slow the train. The

mechanical linkage can become quite elaborate, as it evenly distributes force from one

pressurized air cylinder to 8 or 12 wheels.

The pressurized air comes from an air compressor in the locomotive and is sent from car

to car by a train line made up of pipes beneath each car and hoses between cars. The

principal problem with the straight air braking system is that any separation between

hoses and pipes causes loss of air pressure and hence the loss of the force applying the

brakes.

An air brake is a conveyance braking system actuated by compressed air. Modern trains

rely upon a fail-safe air brake system that is based upon a design patented by George

Westinghouse on March 5, 1872. The Westinghouse Air Brake Company (WABCO)

was subsequently organized to manufacture and sell Westinghouse's invention. In

various forms, it has been nearly universally adopted.

The Westinghouse system uses air pressure to charge air reservoirs (tanks) on each car.

Full air pressure signals each car to release the brakes. A reduction or loss of air pressure

signals each car to apply its brakes, using the compressed air in its reservoirs.

7.4 AUTO-EMERGENCY BRAKES (AEB)

Auto-Emergency Brakes (AEB) refers to a special system of braking employed on some

ghat sections with steep gradients, notably the Braganza ghat between Kulem and Castle

Rock. With this system, the loco's speed is limited to 30km/h and the brakes are

automatically applied if the loco moves faster than that at any time on the AEB section.

The AEB system is activated by means of a key obtained at the top of the descending

grade (at Castle Rock for the Braganza ghat). The key, which is specific to each loco, is

engaged and turned in the loco, and then removed and handed to the guard of the train

(except for light locos where there is no guard). While the AEB system is activated, the

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loco cannot run faster than 30km/h; the brakes are applied immediately if the speed rises

above that.

When the loco reaches the bottom of the down grade (Kulem at the foothills of the

Braganza ghat), the AEB system is deactivated and the key is handed over to the Station

Master of the station at the bottom of the ghat section (Kulem). From there onwards, the

loco can proceed at normal permissible speeds. The AEB key specific to a loco is

handed over to the loco pilot by the Station Master of the station at the bottom (Kulem)

when the loco is above to ascend the ghat section. The AEB system depends on a speed

sensor attached to the axle generator (tachometer generator) of the locomotive

7.4.1 Braking rheostat

Large air-cooled resistors, located in the roof of the unit, used to dissipate braking power

generated by the traction motors while braking. Also known as "dynamic brake"; in this

application it is used exclusively at high speeds, and combined with wheel brakes as the

speed drops below a predetermined level. Overall they can take up almost half of the

braking energy in stopping a train set from full speed. There are two sets of rheostats,

one for each power pack. Their effective resistance can be modulated by the chopper to

vary braking effort.

7.5 Pneumatic block and wheel brakes

The main compressor is used to fill the air tanks used for the braking system. These

tanks are located underneath the frame of the unit. There are two brake lines running the

length of the train set, as is common for the electro pneumatic brake system used on

most passenger trains. The first, the "principal line", is maintained at a pressure of 8 or 9

atmospheres at all times and is used to fill the auxiliary brake reservoirs on each vehicle

in the trainset. The second, the "general line", modulates the wheel braking level

between full application (3.5 atmospheres) and full release (5 atmospheres).

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CHAPTER 8

8.1 CONTROL SYSTEM OF LOCOMOTIVES & ITS TYPES

A. Speed control unit

B. Power control unit

C. Traction control unit

D. Load control unit

E. Engine control unit

8.2 Speed control unit

For precise speed and load control, Woodward PGE and PG-EV locomotive governors

have been proven in locomotive service throughout the world. A variety of diesel fuel

injection technologies, from simple mechanical injection to the latest in low-emissions,

high-pressure common rail systems, provide reliable service. Electronic engine controls

and rapid control system development tools interface with locomotive control systems to

optimize performance and efficiency. Actuation and valve technology can precisely

control exhaust gas flow, turbocharger boost pressures, air flows, and other processes to

improve power output, efficiency, and emissions. After treatment control units  provide

automatic regeneration of particulate filters and dosing control.

8.3 power control unit

8.3.1 Auxiliary power supply unit

A static converter that generates head-end electrical power for the rest of the train. HEP

("hotel power") is 380V 50Hz, while interior lighting is supplied with 72V DC. Output

of the converter also runs some equipment in the power car: the transformer oil pumps

and cooling fans, the brake rheostat cooling fans, the thyristor cooling fans, etc.

8.3.2 Automatic coupler

The Scharfenberg-type coupler makes pneumatic and electrical connections without

external intervention. It allows to couple two TGV trainsets nose to nose, either for

normal multiple unit operation (even at high speeds) or for towing. When not in use, the

coupler is concealed by two fiberglass clamshell doors that form the nose of the unit.

These can open away to each side to reveal the coupler.

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8.3.3 Impact absorption block

It is an impact shield to defend the cab cubicle. The deformation of this thick aluminum

honeycomb block absorbs a part of the collision energy if a large object is struck.

8.4 Traction control unit

Train Control Systems are fundamental to the safety and efficiency of the modern

railway system. Hima-Sella, through our expert engineers and staff, is working to

provide the very latest thinking in the field. Using emerging technologies and the best

product partners we install systems that deliver safety with a flexible approach

8.4.1 Runback Protection

We designed to prevent a train from rolling backwards, having reached its destination.

The design meets the requirements of Safety Integrity Level 2 (SIL2) in accordance with

the IEC 61508 standard for functional safety and includes a data logging facility to

record when faults and runback conditions occur. Runback has been fitted to

underground trains across London.

8.5 Engine control unit

The TECU is a next generation locomotive control system designed to communicate

with new electronic locomotives. The TECU can manage hundreds of digital and analog

inputs and outputs for a locomotive and has features such as traction control and event

recording. The TECU's modular architecture allows it to be easily modified to suit a

variety of different locomotives, from cutting edge multi-engine locomotives, to

conventional diesel-electric locomotives, to street cars. TMV Control Systems has many

years of locomotive control system design experience and is ideally suited to design this

next generation control system

8.5.1 Control Elements

Uses the CAN data bus to control engine RPM and receive engine data for

control, display and diagnostics.

Control the power contactors and main generator excitation for Power and

DB operation.

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Wheel slip/slide control in Power and DB based on axle speed sensors. Creep

control for maximum adhesion.

Engine Stop/Start control, with starter thermal overload protection. (AESS)

Cooling Fan control.

Main generator voltage and current limits for protection.

Main generator field control, with over current trip.

Air Compressor control.

Transition control.

Low water input.

Main Reservoir blow-down (optional)

Built-in-Tests: Locomotive self-load, Contactor test, Relay test, Fan test, etc.

Traction Motor current sensing, limiting and protection

8.6 Mechanical transmission:

The output shaft of the motor is connected to the axle gearbox by a tripod transmission,

using sliding cardan (universal-joint) shafts. This allows a full decoupling of the motor

and wheel dynamics; a transverse displacement of 120 mm (5 inches) is admissible. The

final drive is a gear train that rides on the axle itself and transfers power to the wheels.

This final drive assembly is restrained from rotating with the axle by a reaction linkage.

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CHAPTER-9

9.1 LOCOMOTIVES & ITS TYPES

WAP-4

This 5000 HP locomotive was evolved to meet the requirement of hauling longer trains

of 24 coaches at higher speed up to 130 kmph over Indian railways. This loco is

presently hauling important high-speed trains on Indian Railways. These are six axles

loco with axle and nose suspended drive.

Fig. 9.1 5000 HP 25 KV AC WAP 4 Passenger Electric Locomotive

Table 1

Salient details

System 25 KV, AC, 50 Hz.

Class of Loco WAP-4

Track Gauge 1676 mm (Broad Gauge)

Axle arrangement Co-Co

Brake System Air and Rheostatic

Total weight 112.8 + 1% t.`

Wheel Diameter 1092 mm (New) , 1016 mm (Full worn)

Length over buffers 18794 mm

Panto locked down height 4232.5 mm

Traction Motor type HS 15250A, DC Series Motor

Continuous Power at Wheel Rim 5000 HP

Starting Tractive Effort 30.8 t

Control System Voltage 110 V DC

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WAP-5

WAP-5 class locomotives employ advanced control and propulsion technology and are

capable to deliver 5400 hp on rail. The locomotive has all the hallmarks of a high- speed

propulsion unit viz. light weight, fully suspended drive and disc brake. Though

presently, it has been certified for 160 kmph operation, the locomotive has been

designed to give a service speed of 200 kmph with test speed potential of 225 kmph.

Since IR is currently facing severe competition in Premium Passenger business market

from commercial airlines, sooner or later, IR will have to introduce medium high speed

intercity Passenger Services.

.

Fig. 9.2 5400 HP 25 KV 3 phase Passenger Electric Locomotive

WAP-5

Table 2

System details

Horse Power 5400

Supply system 25 kV, AC, 50 Hz.

Track Gauge 1676 mm (Broad Gauge)

Axle Arrangement Bo-Bo

Total weight 78+ 1%t

Axle Load 19.5 + 2%t.

Wheel Diameter 1092 mm (new ),1016 mm (Full Worn)

Length over buffers 18162 mm

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Panto locked down height 4237 mm

Max. Service Speed 160 kmph

Type of Traction motorsFXA 7059, 3-phase Squirrel Cage Induction

motors

WAP- 7

Intercity and interstate fare friendly Passenger market has of late shown a strong and

sustained growth in recent times. This market needs very powerful Electric locos which

can haul 24 to 26 coaches at speeds in the range of 130/ 140 km/ph. To meet the surging

demands of this amazingly exploding Passenger market segment, CLW has come out

with a 6000 H.P loco premium Electric loco product – WAP-7.WAP-7 class loco is

based on WAG-9 platform and differs from WAG-9 in gear ratio and the control

software.

Fig. 9.3 6000 HP 25 KV 3-phase Passenger Electric Locomotive

WAP-7

Table 3

SYSTEM DETAILS

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Horse power 6000

Supply system 25kV, AC, 50 Hz.

Track gauge 1676 mm (Broad Gauge)

Total weight 123.0 + 1%t.

Wheel Diameter 1092 mm (New ), 1016 mm (Full Worn)

Length over buffers 20562 mm

Panto locked down height 4255 mm

Type of Traction motors 6FRA 6068, 3-phase Squirrel Cage Induction Motors

Continuous Power at wheel rim Horse Power

Starting Tractive effort Supply System

Max. Service Speed Track Gauge

Brake System Air, Regenerative & parking

Drive System 3-phase Drive with GTO Thyristors and

microprocessor based VVVF Control.

WAG- 9

Rail Freight market which is registering a remarkable growth since 2000, has also

triggered buoyancy in demand for Electric Freight locomotives. Almost 60 – 65 % of

IR’s freight handling takes place over IR’s Electrified Golden Quadrilaterals and

Diagonals, though it accounts for only 25 % of its route kilometer range. It give a

starting tractive effort of 460 KN and maximum braking effort of 260 KN. Rated 6000

hp, the loco has also been successfully adapted to give 508 KN of starting tractive effort

with additional ballast.

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This loco also is capable to give 6000 hp on rail upto its rated speed of 100 kmph which

gives superior section clearing capability especially in handling speed restriction.

Fig. 9.4 6000 HP, 25 KV, 3- phase Freight Electric Locomotive

WAG-9

Table 4

SYSTEM DETAILS

Gauge 1676 mm

Continuous HP 6000

Starting Tractive effort 460KN (47t)

Max, Speed 100 kmph

Breaking Air, Regenerative

Wheel Aggangement Co-Co.

System Voltage25KV AC, 50 Hz.

Weight of loco 123 tonne

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