18047730 electric traction

8/13/2019 18047730 Electric Traction

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Suresh Kamble Electrical De t.GPA

ElectricElectric

TractionTraction



Block Diagram of A.C Locomotive

1. Overhead

2.

3. Circuit

4. On-load tap

5.#. $"oothing

%. &.C . Traction



Trolley Wires or Contact wire

Trolley wire or Contact wire



Trolley Wires or Contact wire

Contact



Trolley Wires

The trolley wire or contact wire must be suspended withthe minimum of sag

so that it remains practically horizontal.

So that the contact between the wire & current collectormay be maintained at high speeds.

This is achieved by which the trolley wire(contact wire) issupported by another wire known a the “catenary or“!essenger

The catenary construction are different types". Single catenary construction.#. compund catenary construction



$in le catenar contruction

F

$ steel wire with seven or more strands supports the trolley wireby means of droppers clipped to catenary & trolley wire ate%uidistant horizontal intervals.

The span of catenary wire ' to metres with a sag of

from " to # metres for straight track.

(ig. $ingle catenar'contruction

Contact

Caten

&ropp



$ingle catenar'contruction

$i l i



$ingle catenar'contructioncontd)))

The distance of droppers is between * to ' metres

curved track the spans of shorter length are employed.

Such construction provides for speed upto

*dvanta

Ø It is relatively cheaper.Ø Less maintenance.Ø Single catenary construction is considered

suitable for most light Weight a.c. system.Ø Suitable for secondary routes here traffic



+mployed for heavy current i.e where traffic density is high.

,t consist of three wires.".The upper wire is catenary wire- which is insulated from the

supporting structure#. The another wire known as intermediate catenary- is

supported by droppers clipped to both wires.

*. Third wire i.e trolley wire.

atenary or messenger wire

/ropper ,ntermediatecatenary

Loop

Trolley wireFig. shos compund catenary



ompund catenary ontd0

Trolley wire is suspended from intermediate catenary by solidwire loop droppers which are to slide vertically on theintermediate wire & fi1ed the trolley wire.

The purpose of intermediate catenary- besides increasing thecurrent carrying capacity- is to provide for more uniformity in+lasticity.

The compound catenary is used on lines where speed ranges

is " to ## kmph.



urrent ollector

Current



Current Collector contd…..

The current in the overhead

system is collected with thehelp of sliding contact collector mounted on the roof of thevehicle.

The main re%uirement of current collector is that it should keepontinuous contact with trolley wire at all speeds.

There are three types of current collector

". Trolley collector #. 2ow collector *. 3antograph collector.



Trolley Collector

This collector is used for Tramways & trolley buses & is

mounted on the roof of the vehicle contact with overhead wire.,t is made either grooved wheel or a sliding shoe carried atthe end of a light trolley pole attached to the top of the vehicle& held in contact with overhead wire by means of a spring.

Fig. "rolley ire

1%%% on a double wire



Trolley Collector contd….

The trolley collector is suitable for low speeds upto *# kmph

2eyond this speed there is risk of its 4umping off the overheadcontact wire particularly at points & crossing.

E+peri"ental trolle' bu in 1#$# trolleybus



Bow Collector

,t consist of two roof mounted trolley poles at the ends of whichis placed a light metal strip or bow- about " metre long for current collection

Fig. %o collector "rolley %us



Bow Collector contd….

ollector strip is made of soft material like copper- aluminum or carbon.

,t never wear instead of trolley wire as it is easy to replace collection strip than trolley wire.

The bow collector also operates in the trailing position.5ence- it re%uires provision of the either duplicate bows oran arrangement for reversing the bow for running in the

reverse direction.

2ow collector is not suitable for railway work where speedsup to "# kmph and currents upto *$



Pantograp Collector

The main function is to maintain link between overhead contactwire & power circuit of the locomotive at varying speeds indifferent climate & wind conditions on varying stiffness ofoverhead e%uipments.

6ig show a diamond type single pan pantograph 6ig show a actual diamond type pantograph

P t C ll t td



Pantograp Collector contd…….

6ig show a pantograph collector

$pri

pa

Ø& positive pressure has to be

maintained atall "imes to avoid loss of contact '

sparking.

Ø%ut pressure must be as lo as

Ø It consists of a pantograph frameork of

Ø "he contact portion consists of a pressed steel pan

fitted ith reneable copper earing Strips hich areforced against the

Ø "he pantograph can be raised or loered from cabin by



Desira!le Caracteristics of Traction motor

The main re%uirements of electric motors used for traction work

". #lectric caracteristics$

iii. 5igh starting tor%ue

iv. Simple speed controlv. 3ossibility of electric brakingvi. apacity of withstanding voltage fluctuationsvii. apability of withstanding temporary interruption of supplyviii. 7verload capability

i1. 3arallel running

( i bl !h t i ti f " ti t



%. &ecanical features$

iii. 8obustness & ability to withstand continuous vibrations.

v. The weight of the traction motor should be minimum inorder to increase the pay load capacity of the vehicle.

1. The traction motor must be small inn overall dimensions.

1ii. The traction motor must be totally enclosed type-

to provide protection against dirt- dust- water- mud etc.

(esirable !haracteristics of "raction motor



Traction motor

'one of te motors can ave all te desira!le caracteristics.

".D.C series motors.

).(ingle pase A.C series motors

*.+epulsion motors.

,.Tree-pase nduction motors

/.Linear nduction motors



(uita!ility of D.C series motor for Traction

). D.C series motor develops ig tor0ue at low speeds1 low tor0ue at ig speeds. Tis is te e2actly tere0uirement of traction units.

3. Te field flu2 varies as te armature current4 as in tecase of series motor4 tor0ue corresponding to tegiven armature current. Terefore4 is independent ofline voltage 1 tus unaffected !y te variations in teline voltages.

*. Commutating properties of series motor are also very

good as increases in te armature current as a resultof eavy load tor0ue results in te decrease ofarmature speed. Tis reduces te magnitude of e.m.finduced in te coils under going commutation wicelps in acieving sparkless current collections

Suitability of / series motor for Traction contd



Suitability of /. series motor for Traction contd....

*. In case of dc series motor + upto the point of magneticsaturation+ tor,ue developed in proportional to the s,uare of thecurrent.

"herefore+ dc series motor re,uires comparativelyless increased

poer input ith the increase in load tor,ue. "husthe series motor

are capable of ithstanding e-cessive loads.

. Speed of dc series motor can be controlled by variousmethods.

/. %ecause of lo time constant of field in case of series

Suitability of / series motor for Traction contd



$. "he dc series motor is simple ' robust inconstruction.

#. "he dc series motor+ oing to its characteristics+ ismost

Suitability of /. series motor for Traction contd....

(ra

"he main draback of dc series motor arecommutation

Which restricts speed+ current ' voltage. "herefore is a



(uita!ility of single pase a.c series motor for Traction

1. For a given W rating ac series motor is 1.* to 2

times in sie ' eight of the corresponding dc series motor.

2. "he construction cost of an ac series motor ismuch more than

of a dc series motor.

. "he starting tor,ue of a.csingle phase motor isloer than that

of dc series motor due to poor poer factor at thestart.

(uita!ility of single pase a cseries motor for Traction contd



(uita!ility of single pase a.cseries motor for Traction contd…

*. "he speed of an ac series motor may be controlled

efficientlyby taps on a transformer. Which is not possible in

case of adc series motor.

. 4oever+ single phase ac series motor have betterperformance

on reduced supply fre,uency says 2* 4. "he

higher fre,uency results in higher leakage reactances ' hence a



(uita!ility of Tree pase nduction motor for Traction

ØIt has simple ' robust construction.Ø "rouble free operation.ØLess maintenance.Ø4igh voltage operation conse,uently re,uiringreduced

amount of current.Ø&utomatic regeneration are the main advantages of5ph. Induction motor for traction.

Ø%ut due to their flat speed5 tor,ue characteristics+constant

(uita!ility of Tree pase nduction motor contd



(uita!ility of Tree pase nduction motor. contd…

With the development of thyristorised invertercircuits+it has no been possible to invert the supply

and obtaina variable fre,uency supply hich could be



Power supply Arrangement

Since Indian 6ailays have decided to adopt 2*kv+ *0 4

Folloing arrangements of poer supply to various substations e-ist

1. 7oer is purchased from supply authorities ho areresponsible

for the operation ' maintenance of 128110 kv

transmission lines ' grid substations upto 2* kvout 5 going terminalsof substation.

4oever 2* kv feeder circuit breaker is controlled

2. &ll the 12 kv ' 2* kv e,uipments of substationis oned+

installed operated ' maintained by the supplyauthorities.



C i P f P l



Constituents or Parts of Power supply system

9arious elements of poer supply

1. Sub-station.

3.Feeding posts.

5.Sectioning & paralleling posts.

7.Sub-sectioning & paralleling posts.

9.Sub-sectioning posts.

( ! t ti



(u!station

Fig. layout of a typical traction sub5station.

5eedin ost



5eedin ost

18047730 electric traction

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