railway traction systems

7/15/2019 Railway Traction Systems

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Railway Traction Systems09104007 Anish Nangia

09104011 Anubhav Aggarwal

09104020 Gaurav Manchanda

09104040 Payal Niharika09104050 Sanjoli Jain


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Introduction

Classification

Electric Traction

Railway Traction

Third rail system Overhead system

Contents


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Traction is defined as

a physical process in which atangential force is transmitted across aninterface between two bodies throughdry friction or an intervening fluid film

resulting in motion, stoppage or thetransmission of power


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Traction

Non-Electric

Electric

Classification


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Electrification in traction (in India) is used with three

types of locomotives: Using single phase AC commutator motor

Using DC with tapped transformer and rectifier

Using phase converter and induction motor

Application


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Pros:

High torque-to weight ratio

Regenerative braking is possible

Lesser noise

Less maintenance

Cons:

High Capital cost

Pros & Consof Electric Traction


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Permanent Magnet Motors:

High power density and power factor

High Efficiency

High Cost

Switched Reluctance Machine:

Robust Rotor Structure

High Torque Ripple

Poor Power Factor

Induction Machine

Low Cost

Robust Rotor Structure

Low Power Density

Inferior power factor and efficiency

Motors used for Electric Traction


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Railway Traction

Voltage

Current

DC

AC

Contact System

Third Rail

Overhead

Railway Traction


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Supply for traction systems

DC

Simpler, especially for railwaytraction

Easy control

Easier to maintain

Expensive (for long run) Sparking and corrosion

Unsuitable for regenerativebraking

AC

Efficient and cheaper for longdistances

Less or no maintenance

Reliable

Higher level of adhesion

Complicated control


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Existing Traction Systems use DC motors, because of

the following reasons:1. Less expensive

2. More efficient for some H.P.

3. Rail conductor track system is less costly for DC thanfor AC.

Trends in Traction System


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Advantages of AC motor over DCmotors

Commutators-prone to

fail due to vibration andshock

DC motor not suitable forregenerative braking,requires complex andbulky extra components

DC motors tend to injectharmonics in the system

IM doesnt use

commutators Fairly easy to use

regenerative braking

Simpler construction


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Standard voltage levels

Voltage Type600 V DC

750 V DC

1.5 kV DC

3 kV DC

15 kV AC,16.7 Hz

25 kV AC, 50 Hz


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1500 V DC overhead traction system used around

Mumbai Delhi Metro uses 25 kV AC overhead lines with ground

level and elevated routes

Kolkata Metro- 750 DC third rail

Kolkata trams- 550 DC overhead with undergroundconductors

Railway Traction in India


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Third rail system

Third rail or conductorrail placed alongside therail track.

Generally placed outsidebut sometimes placedinside


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Third rail Systen


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Shoe and Shoegear

Shoe is used to collect

the current on train.

Wherever conductor railsare interrupted, shoe is

given a ramp for smoothtransistion


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Shoegears


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Third rail breaks

Gaps usually leads to the

loss of power

Power loss can belessened by using locating

shoes along the train andconnecting them


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Benefits:

Easier to install

Cheaper

Lesser prone to power surges

Disadvantages:

Hazardous

Weather affected

Practical limit on speed

Benefits and Disadvantages


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Overhead System


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In overhead system, there are overhead lines that

supply electricity Trains collect the electricity through pantograph, bow

collecters or trolley poles

The wire must be weather durable, and withstand

wind

Overhead system


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Catenary

Catenary are overhead

wires that form a supportstructure

Helps maintain the lateraland horizontal tension


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Catenary suspension systems


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Pantograph

Used to collect electricity

Easier to isolate

Contact maintained by

spring or air pressure


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Horns provide balance to the contact wires

They also protect the pantograph from obstructionslike tree limbs etc

The horns have no current conducting function

They are directed downwards so that they dont

tangle with overhead lines

Pantograph Horns


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Single Arm Pantograph:Less power, fault prone

Double Arm Pantograph:More power, fault tolerable

Types of Pantograph


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Block Diagram of Modern AC ElectricLocomotive


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Electro-pneumatic contractor type

High voltage; mounted on the roof of the locomotive

All the OHE are connected/disconnected by themeans of this CB

Circuit-Breaker


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Main Transformer of the locomotive

25kV supply fed to this transformer via main bushing

Winding divided into 32 taps (generally)

Taps attached to tap changer

Loco Transformer


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Tap-Changer


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Schematic of a Single-Phase AC

Steps down the25 kV AC

Converts AC tospecified DCVoltage

Smoothens and

Filters the DCoutput


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This is essentially a bank of capacitor and inductor to

give a smooth DC output It also eliminates/reduces the harmonics produced by

drive converters and traction motors

The capacitor bank in this section can also provide a

small amount of reserve power in the transientsituations, if needed by the traction motors

DC Link


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Inverter with three thyristor based components

Three components produces three phase AC

Thyristor components controlled by microprocessor-can produce a wide range of AC frequency andvoltage

Drive Converter


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AC Electric Locomotive with DCmotor


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Track Magnet

To reduce arcing at

neutral section, trackmagnets are used

Track magnets

automatically switch offthe supply when trainreaches neutral section


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Neutral Section

It is a short section ofinsulated and deadoverhead equipment whichseparates the area fed byadjacent substation orfeeding post.

Neutral Section is alsopresent when DC supplychanges over to AC supply,and the links are joined byonly a neutral section


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Benefits and Disadvantages

Benefits

Robust

Less hazardous

Efficient

Disadvantages

Prone to lightening surges

Capital extensive

May require reconstruction


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Thank youAny queries?

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