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SUBJECT CODE : EE1451STAFF NAME : U.T.TAMIL ARASISTAFF CODE : EE27

ELECTRIC ENERGY GENERATION,

UTILISATION & CONSERVATION

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UNIT IV

ELECTRIC VECHICLE

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INTRODUCTION

Locomotion in which driving force is

obtained from motors

Driving equipment should be capableof overloads for short periods

Maximum tractive effort should be

exerted at starting Wear should be minimum

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Advantages :

Cheapest method

Free from smoke and flue gas

Very high starting torque

Smooth and rapid acceleration andbraking

Adhesion coefficient is better Great passenger carrying capacity

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Classifications :

Railway Electrification

DCsystem

ACsystem

Compositesystem

1 31 toDC

1 to3

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Speed Time curve

Sub urban service

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It consists of

Acceleration period

Free run period

Coasting period

Braking period

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Main line service

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Important terms

Creset speed (Vc)

- maximum speed attained by

train during run

Average speed (Va)

- Distance between stops in kmActual time of run in hour

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Urban service

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Tractive effort is transferred todriving wheel

Tractive torque and effort is given by

T = Fd2

F = 2T

d

d = diameter of gear wheel in metres

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Tractive effort for propulsion of atrain

component needed to provide

acceleration

component needed to overcome

train resistance

component needed to overcomegradients

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Factors affecting specific energyconsumption

Distance between the stops

Maximum speed Weight of the train

Train resistance

Acceleration and retardation

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Teaction motor control

DC series motor control

Series parallel control of DCseries motor

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DC series motor control

At the time of starting, no back emf,

so motor speed is high.

to limit the current, starting

resistance is added.

Some energy is wasted in resistance

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Energy loss diagram

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Series parallel control

two motors are used

at starting they are connected in

series for full speed , they are connected in

parallel

Energy loss is minimum

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Energy loss diagram

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Series parallel starting methods

Shunt or short circuit transitionmethod

Bridge transition method

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Shunt transition methods

Full series

first transition

Second transition

Third transition

First parallel

full parallel

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first series

Full series

Transition

first parallel

full parallel

Bridge transition method

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Full series, first transition and Secondtransition

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Third transition, First parallel& full parallel

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Bridge transition method

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Third transition, First parallel& full parallel

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Recent trends in electric traction

PWM technique is applied

PWM AC drives used in subways, railcars, trolley buses, diesel electric and

electric locomotives.

GTOs are user in PWM invertertechnology

Microprocessors unit controls firingpulses to the GTOs

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Advanced speed control

Tap changer control

Thyristor control

Chopper control

Microprocessor control

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Tap changer control

Variable voltage control without losses

Low voltage tap changing method

- by keeping the number of turns

primary turns and changing the

secondary turns

High voltage tap changing method

- keeping turn ration constant and

applying variable voltage

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Thyristor control

Magnitude of DC voltage is decided

by average of the positive half cycles

allowed to pass through therectifiers

by allowing positive half cycles

by not allowing certain portion of

positive half cycles

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Diagram

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Chopper control

Pulse Width Modulation

- time period constant with variation inTon & Toff

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Microprocessor control

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THANK YOU