application of dc generator at railway coach

THIAGARAJAR COLLEGE OF ENGINEERING (A Govt. Aided, ISO 9001:2008 Certified, Autonomous Institution Affiliated to

Anna University)MADURAI – 625 015Department of Electrical and Electronics Engineering

APPLICATION OF DC GENERATOR

RAILWAY COACHPRESENTED BY,

V.Rajalakshmi -14E87 T.Naveena -14E80R.Priyadharshini -14E85 T.Palani Kumar -14E83 S.P.Nandhini -14E79 P.Prakash -14E84S.Priyanka -14E86 S.Padmanathan -14E82

CONTENT:

OVER VIEW OF DC GENERATOR ELECTRICITY IN RAILWAY SYSTEM DC GENERATOR IN RAILWAY SYSTEM POWER SUPPLY AT RAILWAY SYSTEMTYPES OF POWER GENERATION IN RAILWAY SYSTEM METHODS OF DRIVING THE GENERATORAPPLICATION CONCLUSION

DC GENERATOR:

An dc generator converts mechanical energy to electrical energy.

The energy conversion is based on Faradays Laws of Electromagnetic Induction.

When conductor moves in a magnetic Field in such away that it cuts the magnetic lines of flux and emf is produced

Emf causes current to flow if the conductor circuit is closed.

BASIC OPERATION OF DC GENERATOR:

As the loop rotates, the mag. flux through it changes with time

This induces an emf and current in the external circuit.

The ends of the loop are connected to split rings that rotate with the loop.

Connections to the external circuit are made by stationary brushes in contact with the slip rings.

SIMPLE LOOP GENERATOR: Consider a single turn rectangular copper coil is

rotating in a magnetic field. The coil occupies different angular positions during

its rotation. When the coil is rotated through an angle of 90° the

emf induced in the coil is maximum Rotate the coil further by an angle of 180°.The emf

induced in the coil will be zero. Rotate the coil further by an angle of 270°.The emf

induced in the coil is maximum in the reverse direction.

We conclude that the nature of the emf induced is alternating.

CLASSIFICATION ACCORDING TO EXCITATION:

Separately excited DC generator Self excited DC generator

PARTS OF D.C. GENERATOR:

Yoke Pole core and pole shoe Field coils Armature core Armature winding Commutator Brushes and brush holders Bearings

YOKE: Acts as frame of machine

Mechanical support

Low reluctance of mag. Flux

High reliability For small machines: Cast iron For large machines: Cast steel

ARMATURE: The power-producing component of

an dc generator. The armature can be on either the

rotor or the stator. The windings are placed in slots on

the surface of the armature core It consists of steel or soft iron to

provide a good magnetic path, and laminated to reduce eddy currents.

POLE CORES AND POLE SHOES: POLE CORE: Carry the field coils

-Rectangular cross section-laminated to reduce heat loss-fitted to yoke through bolts

POLE SHOES: Acts as support to field poles and spreads out flux

COMMUTATOR:

Hard drawn Cu bar segments insulated from each other by mica segments

Between armature and external circuit

Split rings(acts as rectifier)

BEARINGS AND BRUSHES: Carbon,Carbon graphite,copper are used to collect current

from commutator

SHAFT AND BEARING: SHAFT: Mechanical link between prime mover and

armature BEARING: For free rotation

ELECTRICITY IN RAILWAY SYSTEM: Electrical energy in railways is required for

traction purpose. Coach lighting, fans, mobile and laptop charger, air conditioning equipment, pumping, hot plates, bottle coolers, water boiler, refrigerators, battery charger for emergency light, radiator motor and distribution transformer, these loads are collectively described as hotel load

DC GENERATOR IN RAILWAY SYSTEM:

TRAIN POWER SYSTEM - Centralized Power Source System - Distributed Power Source System GENERATING EQUIPMENT: Dc Generator, Belt Tension Device, Control Device And Battery

OUTLINE OF THE GENERATING EQUIPMENT:

DC GENERATOR: when the train is stopped, power supplied to the load from the battery. when the train is running , the dc generator supplies power to the load at the same time charges the battery which was discharged when the train was stopped to maintain the battery fully charged state.

OUTLINE OF THE GENERATING EQUIPMENT: BELT TENSION DEVICE: The Dc Generator Suspended From The Under Frame Of The Coach And Driven By The Flat Belt Axle Pulley The Tension Of The Belt Is Maintained Constant With The Help Of Change The Distance Between Center Of The Pulleys CONTROL DEVICE: - Rectifying Device - Generator Voltage Regulator - Lamp Voltage Regulator

POWER SUPPLY:Electric power to railway coach is supplied through.,

Overhead lines DC batteries Generators

INTERNAL STRUCTURE:

OVER HEAD LINE: Power supplied to moving trains

trough continuous conductor running along the track.

This wire suspended from poles are called as catenary wire.

This train picks up the power from wire through pantograph.

DC BATTERIES:

DC batteries in trains acts like power banks. These batteries are charged through the

supply from over head lines and generators in trains.

Batteries are used to provide supply in case of power shortage.

Lithium batteries are commonly used in trains.

Li-ion batteries used in trains

GENERATORS: The generators used in railway coach are basically classified into two Main generators. Auxiliary generators.

MAIN GENERATORS :

These generators are used in propulsion of train. These generators provides supply to traction motor

in train . Hence helpful for the movement of train in initial

stage. Commonly DG sets are used as main generators.

DG SETS:

DG sets stands for diesel generator sets.

The diesel generator is a combination of diesel engine with a electric generator to generate electric energy.

This a specific case of engine generator.

Generator

WORKING –DG SETS:

The fuel (diesel) is fed to the engine. When the engine is started it coverts the chemical energy to

mechanical energy(rotating shaft). The rotating shaft is coupled with the generator and provides the

required mechanical input to the generator. This rotation of shaft in turn rotates the rotor of generator. As the rotor rotates emf is induced and electrical energy is taken as

output,USE: The electrical energy obtained is mainly used as a supply to traction motors used in train.

DG SET:

TYPES OF POWER GENERATION:

Self generation(SG) Mid on generation(MOG) End on generation(EOG) Head on Generation(HOG)

SELF GENERATION: DC Generator is mechanically

coupled with the coach wheel. Due to residual magnetic field

and variable magnetic flux ,voltage is induced in the generator.

The voltage generated is then sent to charge the dc batteries.

SELF GENERATION: ADVANTAGES:• Higher flexibility in rake

formation• Each coach is self- sufficient in

generation• Depending on usage , can be

designed for required capacity

DISADVANTAGES:• poor efficiency – 57%• higher weight affects speed

potential- not suited above 110 kmph

• Maintenance of batteries, axle, pulley- belt as they are subjected to vibration continuously.

LUCKNOW MAIL HAULED BY DIESEL LOCO WDP 4 EMPLOYS SELF GENERATION

MID ON GENERATION(MOG): Supply obtained at 110V

through one power car in the center having 230kVA Diesel generator sets.

Used for trains having frequent stops.

Suitable for slow moving passenger trains.

MID ON GENERATION(MOG): ADVANTAGES:

• Centralized control in all coaches.

• Absence of bulk batteries.

• Reduced maintenance.

DISADVANTAGE:

• Space constraint since one coach has to be dedicated for power generation(power car).

END ON GENERATION: Employs two power cars at both ends of the

train. Power cars fitted with 2x750kVA Diesel

generator sets. Supplies electric energy to individual coaches. A 24V , 90Ah battery is provided under frame

along with battery charger to provide emergency lighting in times of power failure.

USE OF END ON GENERATION(EOG): Mainly used in fully air conditioned trains Presently this system is followed in Rajdhani express Sadhapthi Duranto Garib rath

EOG IN DIESEL LOCOMOTIVE HAULED TRAINS:SHATABDI EXPRESS HAULED BY WDM 3 DIESEL LOCO

DURONTO EXPRESS HAULED BY DIESEL LOCO

POWER CAR OF SHATABDI EXPRESS:

END ON GENERATION: ADVANTAGES:

• Elimination of bulk batteries• Reduced dead weight &

maintenance• High reliability

DISADVANTAGES:

• Higher fuel cost, noise & smoke pollution.

• Reduction in commercial space.• Need for staff to operate &

maintain.

MAINTENANCE STAFF INSIDE POWER CAR:

HEAD ON GENERATION(HOG): In this system, power is provided from the locomotive at

the head of the train. Electric locomotives derive power from overhead supply

lines. Power produced is 4500kW. The power produced is

supplied to all loads in AC, Non- AC coaches. Diesel locomotives use a separate Diesel generator sets

to generate electric power. Diesel locomotives have been widely replaced by electric locomotives.

USES: Currently used in Saptagiri express running between Chennai and

Tirupati electrified line, power supply for lighting load of 35kW is derived from HOG.

Most widely used in all trains of Northern railways, Central Railways, South central railways, Southern railways, West Central railways, Eastern railways.

Employed in Pandian, Vaigai, Nellai, Intercity express and many other trains in TN.

These trains are hauled by WAP 7 electric locomotive capable of delivering 4500kW power

VAIGAI EXPRESS HAULED BY DIESEL LOCOMOTIVE:

TRAINS HAULED BY WAP7 ELECTRIC LOCOMOTIVE:

Vaigai express Nellai express

HEAD ON GENERATION(HOG): ADVANTAGES:

• Pollution free• Cost of power production per

unit is 25% cheaper than EOG & SG

• More commercial space available due to elimination of power cars.

DISADVANTAGE:• Power interruption of short

duration.

METHODS OF DRIVING THE GENERATOR: Carbon shaft arrangementBy mounting generator on mid axleBelt driven

CARBON SHAFT ARRANGEMENT:

Carbon- shaft driven by gear box mounted on axle of wheel. Generator mounted on coach under frame .

REASON FOR FAILURE: CARBON SHAFT METHOD

FAILED DUE TO THE FOLLOWING REASONS:

• Breakage of carbon shaft & gear box.

• Failure of fasteners used for coupling

• Jamming of carbon shaft arrangement

Damaged gear box

MOUNTING ALTERNATOR ON MID AXLE:

Rotor fitted directly on the axle of the wheel itself. Stator is in two halves and provided on the axle with the help of split bearings & held in position with a reaction rod. No belt driven mechanism. This method too was unsuccessful. Defects were:• Damage Of Bearings• Grease Leakage• Breakage Of Terminal Box • Accumulation Of Copper Dust

MID AXLE PERMANENT MAGNET ALTERNATOR:

BELT DRIVEN PERMANENT MAGNET GENERATOR:

Reduction in size of rotor due to use of permanent magnet instead of field windings.

Overall reduction in size, weight possible. It is efficient & durable.

AUXILIARY GENERATORS:Auxiliary generators are generators that provide electrical supply to secondary applications in train such as Fan Lighting Mobile and laptop charging .

APPLICATIONCARRIAGE LIGHTING: Generator the traditional source for on-board low voltage

supplies. The generator is a DC machine driven by the diesel engine or, on electric locomotive (train), by a motor powered from the traction current supply. On a coach, the generator was often driven directly off an axle (a dynamo), batteries providing power for lighting when the train was stationary

CARRIAGE FAN: 400 mm, 300 mm and 200 mm sweep

carriage fans are used on Indian Railways in SG, MOG, and EOG coaches where the system voltage could be DC 110 V . As a passenger amenity item, carriage fans have to be maintained in such working condition as to obtain good air flow and trouble free service for ensuring maximum passenger satisfaction

REGENERATIVE BRAKING:

During braking, the traction motor connections are altered to turn them into electrical generators

The motor fields are connected across the main traction generator (MG) and the motor armatures are connected across the load.

The rolling locomotive or multiple unit wheels turn the motor armatures, and the motors act as generators.

The energy generated in generator may be used in two ways

REGENERATIVE BRAKING:The generated energy is sent back to recharge the batteries.

DYNAMIC BRAKING:The generated energy is sent to the resistor grids in the roof of the train and is dissipated as heat.

BEGIN WITH END IN MIND