Traction Introduction

8/19/2019 Traction Introduction

1/21

What is electric traction?

Electric traction is meant for locomotion in which thedriving (tractive) force is obtained from electric motors

(called as traction motors). It involves utilization of electric power for traction systems

i.e., for railways, trams, trolleys etc.

or traction purposes mostly !"#hase Induction motors andd.c series motors are used and both have high starting

tor$ue, prevailing re$uirement for the high speed

What’s it allabout?


2/21

%he year &''& saw the birth of the rst electric ailway

run by a *erman Engineer Werner +an iemens using boththe rails to carry the current. inding this a little toodangerous, iemens soon adopted the overhead electricwires.

Electric traction was introduced on Indian ailways in

year &-/ on &./ 0+ 12 and the rst electric trainran between 3ombay4s +ictoria %erminus and 0urla alongthe 5arbour 6ine of 2, on ebruary !, &-/, a distance of-./ miles, 7agged o8 the then *overnor of 3ombay ir6eslie 9rme Wilson.

%he rst actual train run (apart from trial runs) using /:+;2 was on 1ecember &/, &-/-, on the 0endposi"a 5z ;2 traction based on rench ailway (2)

technology. %he @umbai region is the last bastion of &/>>+ 12

; 3rief 5istory %o Electric %raction


3/21

Italian ailways were the rst in the world to introduce

the electric traction. %he world4s rst ;2 locomotive in +altelina, northern Italy

(&'-'A&->).#ower supplyB !"phase &/ 5z ;2, !>>> + (;2 motor

=> :mDh).

It was designed by a5ungary company.

%he &> :m +altellina line was opened on

F eptember &->.

irst ;26ocomotive


4/21

%ypical +oltages used for electric %raction are &./:+ 12

and /:+ ;2 for mainline trains. 2alcutta had an overhead !:+ 12 system until the 4>s.

%he 2alcutta @etro uses =/>+ 12 traction with a third"rail mechanism for delivering the electricity to theE@Gs (Electric @ultiple Gnits).

%he 2alcutta trams use //>+ 12 with an overhead line(catenary) system with underground return conductors.

%he catenary is at a negative potential.

%he 1elhi @etro uses /:+ ;2 overhead traction with a

catenary system on the ground"level and elevatedroutes, and uses a rather unusual 4rigid catenary4 oroverhead power rail in the underground tunnel sections.

ailway authorities purchases the power from thesupply authorities

and they give voltage supply of &!D&&> 0+ atsubstation.

+oltages Gsed or Electric %ractionIn India


5/21


6/21

12 traction units use direct current drawn from either a

conductor rail or an overhead line. %he most popular line voltages for overhead wire supply

systems A &/>>+ 12 and !>>>+ 12. >>+ 12A=/>+ 12 volt range used for third rail

systems (a means of providing electric power to

a railway train, through a semi"continuous rigidconductor placed alongside or between the rails ofa railway trac: and that additional rail is

called conductor rail) 1isadvantages" eHpensive substations are re$uired

at fre$uent intervals and the overhead wire or third rail must be relatively large and heavy. %he low"voltage, series"wound, direct"current

motor is well suited to railroad traction, beingsimple to construct and easy to control.

12 %raction


7/21

;2 %raction units draw alternating current from an overhead

line. %ypical +oltages Gsed areB"

&/ :+ ;2, & 5z (&.= 5z)

/ :+ ;2, /> 5z

/ :+ ;2, > 5z

ewer substations are re$uired and the lighter overhead current supply wire can be used educed weight of support

structure

educed capital cost ofelectrication

;2 %raction

W;*"-ated #ower"/>>> 5#

%raction ystem" /0+ ;2peed" &F> 0mDhr

%raction @otor" 12 @otor


8/21

3ecause of the variety of railway electrication

systems, which can vary even within a country, trainsoften have to pass from one system to another. 9neway to accomplish this is by changing locomotives atthe switching stations.

%hese stations have overhead wires that can be

switched from one voltage to another and so the trainarrives with one locomotive and then departs withanother.

9ften, this is inconvenient and time"consuming ;notherway is to use multi-system locomotives that can

operate under several di8erent voltages and currenttypes.

In Europe, it is common to use four"systemlocomotives (&./ :+ 12, ! :+ 12, &/ :+ & 5z ;2,/ :+, /> 5z ;2)

@ultiystems


9/21

5igh power"to"weight ratio than forms of traction such as diesel

or steam that generate power re$uiring on board prime mover. higher power"to"weight ratio, resulting in

ewer locomotives aster acceleration 5igher practical limit of power 5igher limit of speed

5igher hauling capability o eHhaust fumes or carbon emissions 6ess noise pollution ($uieter operation) %he maintenance cost of an electric locomotive is nearly />J

of that for a steam locomotive. @oreover, the maintenance

time is also much less. ;n electric locomotive can be started at a momentKs notice

whereas a steam locomotive re$uires two hours to heat up. %he motors used in electric traction have a very high starting

tor$ue. 5ence, it is possible to achieve higher acceleration of&./ to ./ :mDhDs as against >. to >.' :mDhDs in steam traction.

;dvantages of ;2 %ractionystems


10/21

It is possible to use regenerative bra:ing in electric traction

system. It leads to the following advantages. ;bout '>J of the energy ta:en from the supply during

ascent is returned to it during descent. ;nd presentlythis returned energy is not sent bac: to public networ:but made available for other vehicles within the networ:

*oods traLc on gradient become safer and speedier. ince height of an electric locomotive is much less than

that of a steam locomotive, its centre of gravity iscomparatively low. %his fact enables an electric locomotiveto negotiate curves at higher speeds $uite safely.

electric trains may be powered from a number of di8erentsources of energy (e.g. hydroelectricity, nuclear, naturalgas, wind generation etc.) as opposed to diesel trains thatare reliant on oil.

electric trains do not have to carry around the weight oftheir fuel unli:e diesel traction.

; fully electried railway has no need to switch between

;dvantages of ;2 %ractionystems


11/21

ignicant capital cost of electrication

Increased maintenance cost of the lines

9verhead wires further limit the clearance in tunnels

Gpgrading brings signicant cost,

especially where tunnels and bridges and other

obstructions have to be alteredfor clearance

ailway %raction needs immune power, with no cuts,warranting duplication of %ransmission and 1istributionsystems, which obviously comes at a #remium #rice.

1isadvantages of ;2 %ractionystems


12/21


13/21

#rovided for speeds upto&>:mph

pan of catenary wire F/"->m

and sag of &"m. elatively 2heaper 6ess @aintenance uitable where traLc density

and operating speeds are

low.

ingle 2atenary

2onstruction

2ompound 2atenary

2onstruction

#rovided for speeds ranges&->"F:mph

;dditional wire calledintermediate wire is used toincrease current carryingcapacity i.e., to haveincreased traLc density.

ystem of %rac: Electrication


14/21

Single CatenaryConstruction


15/21


16/21

3ow 2ollector" It uses a light metal strip or bow about &

m long for current collection. ot suitable for railway wor:

re$uiring speed of &>:mph and higher. e$uires reversing arrangement of the bow

#antograph 2ollector" @ain function is tomaintain the lin: between overheadcontact wire and power circuit of thelocomotive at varying speeds in di8erent

climate and wind conditions %his can be lowered or raised from cabin by air cylinders.

Pa

n

ystem of %rac: Electrication


17/21

1.2 eries @otors" 1evelops high tor$ue at low speeds

and low tor$ue at high speed, eHact re$uirement of thetraction units.

%or$ue is independent of the line voltage and thusuna8ected by the variations in the line voltage.

ingle phase ;.2 eries @otors" tarting tor$ue is lower

than dc series motor due to poor power factor at starting %his motor has surpassed the d.c series motor in terms

of size, weight cost for the same rating.

@aHimum operating voltage is limited to F>> +olts. %hree #hase Induction @otors" #rovides constant speed

operation, developing low starting tor$ue drawing highstarting current and complicated control networ:s ma:esit unsuitable for electric traction wor:.

;utomatic regeneration is the main advantage in

electric traction with this motor.

%raction @otors


18/21

Individual coaches are powered by aHle"driven generators

which charge storage batteries that power lights, fansand other electrical ttings.

9lder coaches use ban:s of F+ batteries while &&>+ innewer coaches.

or powering air"conditioning e$uipment, an inverter was

used to convert the 12 output of a set of batteries toF&/+ ;2. or some time now, however, groups of &&>+alternators delivering &'":W each have been used topower air"conditioning e$uipment (the voltage is steppedup to F&/+).

In @any air"conditioned coaches, a 4mid"on generator4(@9*) is usedM this is a F&/+ !"phase alternator (either inone of the coaches or in a separate 4power"car4), theoutput from which is used both for the air"conditioning,and (stepped down to &&>+) for the lights and fans.

%rain 6ightningD;ir2onditioning(%6D;2)


19/21

ow a days magnetic traction is being used in bullet

trains (also called as Nhin:ansenK" high speed networ:of railway lines) operated by four Oapan ailways *roup2ompanies, comprising over F>> :m of lines with maH.speeds of F>"!>>:mDh.

%est runs have reached FF! :mDh (=/ mph) for

conventional rail in &--, and up to a world record/'& :mDh (!& mph) for maglev trainsets in >>!. Gses a /,>>> + ;2 overhead power supply. ;nnual #assenger traLc of over !>> million per year with

an economic impact of P/>> billion per year.

hin:ansen4s average arrival time was within siH secondsof the scheduled time including all natural and humanaccidents and errors.

hin:ansen trains are electric multiple unit style, o8eringhigh acceleration and deceleration.

%he hin:ansen employs an ;%2 (;utomatic %rain2ontrol) system, manages all train operations, and all

6eading %raction ystem


20/21


21/21

Than"

#ouS 9 T9G;%%E%I9

Documents

Traction Introduction