All about Electric Locomotives of Indian Railways

Electric Locomotives of India:-

Electric Locomotives as the name suggests are driven by Electric energy which is fed by Railway Authorized power stations which goes to Locomotives through OHE wire. 25 KV single-phase supply is provided by power stations which is used by Locomotives after reducing it to 110 V to 1100 Volts by a step-down auto  Transformer.

The first electric train run in India on 3rd February 1925 with conventional Electric Locomotives under the rule of the British Government. After that India started to make its locomotives in India.

Types of Electric Locomotives of India:- 

 Nowadays mainly three types of Electric Locomotives are being used in Indian Railway: 1) Conventional Locomotives, 2) ABB Locomotives, and 3) Alstom Locomotive.

Conventional Locomotives

These Locomotives are the oldest Locomotives and shown in Fig. 1 and Fig. 2.

Fig. 1 Passenger Locomotive
Fig. 2 Good Locomotive

Above two Locomotives are conventional type Electric Locomotives in which first one serial number 22699 is a passenger train loco named as WAP-4 and second one serial number 23531 Valsad Shed locomotive named as WAG-5. Conventional Locomotives  come under 230xx, 240xx, 270xx , 280xx, and 220xx series. These are called by names WAG-5, WAG-7,WAP-1 and WAP-4 respectively.

Where W means broad gauge, A means Alternating Current operated and G means used for goods service & P means used for passenger service. WAP locos are used for passenger trains and WAG locos are used for goods train working. Goods Locomotives maximum operating speed is 100 KMPH and passenger Locomotives is 140 KMPH.  25 KV supply is fed from OHE to Locomotives through Panto and Air Blast Circuit Breaker to Loco step down transformer (HETT3900 and HETT5400), Transformer supply goes to a bridge rectifier to convert ac into dc then goes through smoothing reactors to convert pulsating dc into smooth dc then goes to dc series motor (HS15250A and TAO 659). Conventional Locomotives are driven by DC series motor and operate by 700 to 750 Volts & 700 to 950 Ampere current with Engine Horse power of 4620 HP to 5000 HP.

Speed of dc series motor is controlled by armature voltage control method from zero to normal value and by flux control method from normal to high value. For cooling of Transformer and traction motors three phase squirrel cage induction motors are used and three phase 415 Volts supply is generated by a electromotive device named ARNO, which consists of a single phase induction motor and 3 phase synchronous generator assembly. Current controlling is done by wire wound resistors which are cooled by air blasting. In some modified Locomotives 3 phase 415 volt supply is produced by a static converter (SIV-180 KVA) which consists a AC to DC converter, DC to DC converter  and a DC to 3 phase AC converter.

ABB (Asea Brown Boveri) Locomotives

These Locomotives are most advanced Locomotives used in high speed trains with speed limit 100 kmph to 160 kmph. In these Locomotives 6531 KVA and 7475 KVA transformers are used to step down 25 KV voltage to 1269 Volt. These 1269 Volt single phase AC is given to traction converters which consists of three main circuits namely line converter, DC link and Drive converter. The line converter convert single phase AC to pulsating DC, DC link smooths this pulsating DC and also acts as buffer to fulfill current requirements according to motor loads, and Drive converter convert this smooth DC to 2180 Volt three phase AC which is fed to three phase squirrel cage induction motors. Variable voltage and variable frequency control is used to control the speed of Induction motors. ABB Locomotives weight lies between 78 tons to 135 tons, horse power is from 5442 HP to 9000 HP. These Locomotives comes under 30×××, 31×××,32×××, 37××× and 41××× series.

Fig. 3 WAP-7

Fig. 4 WAP-5

Fig. 5 WAG-9

Above image shows ABB Locomotives in which first one is WAP-7, Second one is WAP-5 and third one is WAG-9  locomotive. W denotes broad gauge, A denotes electric current, P denotes Passenger service or Express service and G denotes goods service. In this way first locomotive is Passenger or Express train electric locomotive used in broad gauge rail. For cooling of Transformer and traction converter air blast cooling and oil/water cooling is used. To generate 3 phase supply we use Auxiliary Converter with same configuration as Traction Converter but produce 3 phase 415 Volt to drive 3 phase Auxiliary motors. All the movements are controlled by microprocessor with the help of sensors and relays.

Alstom Electric Locomotives

These Locomotives are taken from France Country for goods train operations mainly for heavy loads and python type long goods trains. These Locomotives hauling power is (12000HP) maximum among presently available locomotives and can run up to 100 KMPH speed. This is basically a coupled WAP-5 ABB Locomotive type in which two Locomotives are connected back to back to get more power. 

Fig. 6 WAG

You can see in image WAG-12 written on locomotive which means this locomotive is an electric locomotive used for goods service in broad gauge rail and it has horse power 12000 HP. 60××× is series of locomotive and this is the first locomotive of this series. 


Locomotives has no steering, loco pilot only moves and stop the locomotive. Movements of locomotives are controlled by station master as per controller instructions.

Author:- Amarjeet Singh Jamwal authored articles on Basic Electronics EngineeringElectric Traction, and Electronics Practical for INFO4EEE Website

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