traction ppt

7/30/2019 traction ppt

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University College Of Engineering

Rajasthan Technical University

Submitted To:-Shri S.C. Mittal Sir

Associate Professor

Electrical Engineering)

Submitted By:- yogesh09/066

Final Year

SEMINAR PRESENTATION ON ELECRIC TRACTION


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CONTENTS INTRODUCTION

AC LOCOMOTIVE

CONTROL WIRES CURRENT COLLECTOR

TRACTION MOTORS

POWER SUPPLY ARRANGEMENT


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INTRODUCTION

The action of drawing or pulling trains over a trackusing electric power called electric traction.

The traction system may be direct current system or acsystem.


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Trolley Wires

The trolley wire or contact wire must be suspendedwith the minimum sag so that it remains horizontal.

So that the contact between the wire and current

collector may be maintained at high speed.

This is achieved when the trolley wire is supported bythe catenary wire.

Catenary wire may be single Catenary or suspendedCatenary construction


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A steel wire with seven or more strands supported thetrolley wire with the help of droppers.


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The span of catenary wire 45 to 90 meters with a sag of1 to 2 meters from straight track.

The distance between droppers is 3 to 5 meters.

Such construction provides for speed upto 120 kmph .


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CURRENT COLLECTOR The current in the overhead system is collected with

the help of sliding contact collector mounted on theroof of the vehicle.

The main requirement of current collector is that it

should keep continuous contact with trolley wire at allspeed.

There are three types of current collector :

Trolley collector

Bow collector

Pantograph collector


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TRACTION MOTOR

The following types of motor are used in tractionsystem.

DC series motor

Single phase AC series motor

Three phase Induction motor


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Desirable characteristics of Traction

motor The main requirement of electric motor used for

traction work

1 Electric characteristics:

High starting torque

Simple speed control

Possibility of electric braking

Overload capacity


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Mechanical features

Robustness and ability to withstand vibration

The weight of the motor should be minimum in orderto increase the payload capacity of the vehicle

The motor should be totally enclosed type to provide

protection against dirt, dust and water.


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Suitability of DC series motor for

tractionDC series motor develops high torque at low speed.

In case of dc series motor, the torque developed isproportional to the square of the current.

Therefore dc series motor required less increase powerinput with the increases in load torque.


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Dc series motor is simple and robust in construction

It is most suitable for urban and suburban areas wherehigh rate of acceleration is required.


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DRAWBACK

The main drawback of dc series motor arecommutation which restrict speed, current and voltagesince there is a risk of f lashover.


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Suitability of single phase ac series

motor for tractionFor a given KW rating ac series motor is 1.5 to 2 times

in size and weight of dc series motor.

The construction cost of the ac series is more than dcseries motor.

The starting torque of ac series motor is lower than the

dc series motor due to poor power factor at start.Ac series motor is not suitable for urban and suburban

services ,it require high acceleration . However it isextensively used in main line services.


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The speed of ac series motor controlled by efficientlyby taps on a transformer. Which is not possible in caseof a dc series motor .

The maximum operating voltage is limited by 400volts.

Single phase ac series motor has better performance onreduced supply frequency say 25 Hz. The higher

frequency results in higher leakage reactance andhence relatively poor power factor.


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Suitability of three phase induction

motor for tractionIt has a simple and robust construction.

Trouble free operation.

Less maintenance.

Automatic regeneration are the main advantage ofthree phase induction motor.

But due to there flat speed torque characteristics ,

constant speed operation, developing high startingtorque, drawing high starting current they are notsuitable for traction work.


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Power supply arrangement Indian railways have decided to adopted 25 kv,50Hz

power supply

Power is purchases from supply authorities who areresponsible for the operation and maintenance of132/110 kv transmission lines and grid substations upto25 kv outgoing terminals of substation.

All the 132 and 25 kv equipment of substation isowned, installed , operated and maintenance by thesupply authorities.


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However 25 kv circuit breaker are owned, installed ,operated and maintenance by the railway authorities.

But supply authorities will give only voltage supply of132/110 kv at the substation.


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THANK YOU

traction ppt

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