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types of traction in Indian Railways.  
3 Answers
Oct 27 2012 (10:25AM)

Entry# 1328     
types of traction in Indian Railways.

Oct 25 2012 (3:16PM)
Blog Post# 560538-75     
दक्षिण मध्य रेल राही   Added by: VijayAditya*  Oct 27 2012 (10:25AM)
Two types of power systems are used in OHE systems of Indian Railways electrified sections for operations, they are 1.5KV DC supply and 25KV AC supply, the latter being more widely used than the former and DC traction all set to be phased out soon, with WR turning totally AC now. The OHE power is useless unless we bring an electric loco to use it, so lets get to it now:
ELECTRIC LOCOMOTIVES: I have mentioned earlier that diesel locos we usually see are nothing but a
huge diesel generated mounted on the bogies only to provide electricity to the relatively smaller traction motors fixed to the wheels, in that case work had to be done to rotate the alternator hence the bulky size whereas electricity is already available in Electric Locos with OHE wires above yet they are quite large too.
That is because the OHE catenary supplies only single phase AC of 25Kv, voltage needs to be regulated and Rectified to DC to be supplied to ttraction motors in many Locos, Modern three phase locos however use three phase AC(WAP-7, WAG-9 etc) which is produced after conversion of single phase OHE AC to 3 phase using a thyristor conversion system, the use and accecability of 3 phase locos have increased with the wide spread use of solid state equipment for an efficient manipulation of physical elements of dynamic electron movement.
DC Locos are similar to AC ones with a few changes, pole shoes on the Pantograph needed to be thick and strong due to the strong DC current. I hope many of you are aware of the unidirectional propagative character of DC whereas AC is bi-directional hence DC current gives a powerful jolt when passed through a human body while AC throws you away. DC is fed to the traction motors after required manipulation.
It has to be noted that an electric locomotive or any household electric equipment would not work if there is no possibility for electricity to return. In case of Electric Locomotives return current is through the wheels to the rails therefore getting grounded. This is a continuous process, if continuity ceases to exist between locomotive and ground it wouldn’t run. This is ensured by metallic conductive strips being placed in periodic intervals connecting OHE poles and the Rail, therefore current returns through the metallic OHE pole in this case.
Railfanning Note: Metallic strips can be observed at many OHE poles connecting the bottom of the pole to the rail. These long metallic strips of width say 1.5 inch are used as a medium for return current.
To be continued..

Oct 25 2012 (4:42PM)
Blog Post# 560538-85     
aliasloadfailed   Added by: VijayAditya*  Oct 27 2012 (10:25AM)
One addition to this, huge size and weight of electric loco is not only due to electronics for converting AC to DC or to make 3 phases AC in case of WAP5/7 and WAG-9. There is a huge transformer that is there to make the OHE voltage to correct operating level. OHE supply is never in the range of claimed 25KV, it is off by huge margin, to be tune of up to 7000V on negative side or up to 4000V on positive side in receptive OHE type.
Source: Engineering department of

Oct 25 2012 (8:52PM)
Blog Post# 560538-88     
दक्षिण मध्य रेल राही   Added by: VijayAditya*  Oct 27 2012 (10:26AM)
Will get to MU operation with multiple locos only in lead, Lead-Mid, Lead-Aft later.
Multiple Unit: A form where tractive power is derived from one or more places of a rake.
There are a few passenger multiple unit trains which function as local services, a short notes on them:
is a type of diesel powered multiple unit with a hydraulic transmission to move the rake hence called Diesel Hydraulic Multiple Unit. This type however tends to be short.
Ex: DHMU's can be found around SC area serving as local trains usually of three cars with cabs at either ends but only one power car. I remember a distinct voilet colored one and a green one MUE'd to form a six car DHMU once between Manoharabad-SC right after GC when MG trains were running between NZB-Manoharabad.
DEMU-The more recent kind, traction is similar to that of a Diesel-Electric Locomotive; a diesel run alternator powering traction motors, this usually has two power cabs at either ends and rake size varies.
Ex: can be found around Bangalore,Madgaon,SC and many places in IR.
EMU- An electrical multiple unit which operates in similar fashion to that of an AC locomotive. There are however DC run EMU's in CR as Local trains.
MEMU- Mainline Electrical multiple units with enhanced Rating, modified gear ratio and longer endurance fit for Mainline operations.
Railfanning Note: If you are travelling in a power car of EMU/MEMU you can observe a distinct floor mill kinda noise starting all of a sudden, exisiting for a few moments and ending abruptly. This noise is made by the compressor which creates air to power the braking system as trans these days work on air braking unlike vaccum braking earlier.
This Noise can be observed in Diesel and Mainline Electric locomotives as well if you stand close to an idling engine. The Compressor of a WAP-7 loco is at the side of the loco clinging underneath behind the driver CAB, visible from outside. you may find it interesting to observe it next time..
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