….let's share our railways knowledge

History of Electric Locomotive over Indian Railways

By on November 23, 2013

Electric Traction on Indian Railways started with 1500V DC traction and therefore initial Locomotives finding place on Indian Railway maps were only DC Locomotive. The development of locos on Indian Railways thus started.   Traction voltage system started from 1500V DC, 3000V DC in Howrah Division of Eastern Railway for short period before converting into 25kV AC and finally 25kV AC. At present 1500V DC system also is on the last leg of conversion into 25kV AC system over Central Railway thus paving way for uni-voltage system on Indian Railway.

Following major factors accounts for all the historical developments of Electric Locomotive over Indian Railways with development of technologies and demand for speed and hauling capacity.

Voltage 750V/1500V/3000V DC or 25kV AC
Power Converter Excitron Tube/ Ignitron Tube/Silicon Rectifier/Silicon Controlled Rectifier/GTO/IGBT
Traction Motor  DC or 3 Phase Induction Motor; Fully suspended or Axle hung nose suspended; plain sleeve or roller bearing suspension
Braking system (Vacuum Brake for trailing and air brake for locomotive; Air brake for trailing stock and locomotive; Rheostat or Regenerative Braking; parking Brakes
Suspension system Primary and secondary suspension, Helical and rubber sandwich suspension, Hydraulic dampers
Passenger –  Speed and  level of train loads 110 kmph (WAG1, WAM1, WAM4)140 Kmph (WAP1,3), 160Kmph (WAP4,P7)180 Kmph (WAP5)
Freight trains  heavy haul and speed

Loco Numbering system on Indian Railways

The first letter -Gauge

W-Indian broad gauge –  (The “W” Stands for Wide Gauge – 5 Feet 6 inches), Y-metre gauge (The “Y” stands for Yard Gauge – 3 Feet or 1000mm), Z-narrow gauge(2 ft 6 in), N-narrow gauge (2 ft)

The second letter -Type of Traction

D-Diesel – C-DC electric – Built for Mumbai area operation but now CA class only exists. The last to become history is WCG2, A-AC electric (can run under AC traction only), CA-Both DC and AC specifically built to avoid change of traction at unsuitable place for Mumbai area of Central and Western Railway. This class will be historical shortly as soon as Central Railway fully changes over to AC Traction, B-Battery electric locomotive – Two nos available for shunting work in underground Kolkata Metro Railway

The third letter -Services

G-goods, P-passenger, M-Mixed; both goods and passenger, S-Used for shunting – there is no electric loco developed exclusively for the purpose of shunting, U-Electric multiple units, R-Railcars

Therefore, WAG7 shall mean-

“W” means broad gauge

“A” mean AC electric traction motive power

“G” means suitable for Freight service

“7” denotes that this locomotive is chronologically the seventh electric locomotive model used by the railways for freight service.

 History of Developments of Locomotive over Indian Railways

Development of Electric Locomotive can be precisely identified in four distinct periods as 1925-57, 1958-71, 1971-1988, 1989-current and what is in store for future



Year 1925 was the foundation laying period of Electric Traction on Indian Railways. On Feb 3, Harbour branch of the erstwhile GIPR from Victoria Terminus (now called CST) to Kurla 16 Km was the first electrify on 1500V DC and EMUs procured from Cammell Laird and Uerdingenwagonfabrik were used. During the same month, the first electric loco EF/1 (later WCG-1) “crocodile” was introduced.

This was the period of DC traction but electrified only 529 RKM.  Electrification was confined mainly to Mumbai Sub-urban area. Traffic density of sub-urban area associated with ghat section of Karjat-Pune and Kasara-Igatpur justified the need for electrification of this section. Historical documentations related to justification of electrification of these sections



Thereafter, electrification progressed very fast and the  section upto Pune and Igatpuri energized in 1926 and from Colaba to Borivilli in 1928 and finally completed upto Virar in 1936.

The work on Madras MG sub-urban section upto Tambaram started in 1928 and completed on May 11, 1931 with 1500V DC traction and introduction of MG EMU services. The section was later on converted into 25kV AC system in the year 1965.


Electrification of Sheoraphulli–Tarakeshwar branch 142 km of Eastern Railway on 3000V DC completed in Nov. 1957. The operation was limited to EMU operation only and 3000V DC locos procured for operation on this line was suitably converted to operate on 1500V DC system in Mumbai Sub-urban area. This section later on converted into 25kV AC in the year 1967.


With AC traction coming up beyond Igatpuri, it became necessary to develop dual voltage locomotive with different versions following the development of AC locos.





On the recommendations of SNCF, 25kV AC traction was decided as standard voltage for undertaking electrification and also chosen as technical consultant.

An organization called the Main Line Electrification Project — which later became the Railway Electrification Project and still later the Central Organization for Railway came into existence to undertake Railway Electrification works over Indian Raiwlays.


“Mixed Traffic” locomotives were ordered from European 50 cycle Group (a consortium of 8 manufacturers of electrical loco equipment in France,

Germany, Belgium and Switzerland associated with 4 mechanical locomotive builders).100 units WAM1 Nos. 20200 to 20299 were imported from the above said Group and 10 units WAM2 nos. 20300 to 20309 from Mitsubishi Ltd, Japan. The locomotive no WAM1 20250 was shipped to India immediately and commissioned at Kendposi on 12 Dec 1959. With this started the first   25kV AC locomotive series of WAG and WAM class. The details are as follows:


WAM1 (1959-60) : 2800HP SNCF design and manufactured by Kraus-Maffei, Krupp, SFAC, La Brugeoise & Nivelle ( 50 cycle European Group), 74 Tonne, 25 T starting tractive effort and maximum speed of 112kmph,  4 Nos. 575kW/1250V, water cooled Ignitron Rectifier; Siemens/ACEC/Alstom MG 710A – 740hp, 1250V, 480 A, 1000rpm weighing 2750 kg fully suspended force ventilated traction motor; Jeumont Transformer with 20 taps, B-B monomotor bogies, Jacquemin drive with pendular suspension and equalizer beams; Air brake for self and vacuum brake for trailing stock.

This locomotive worked well except initial problem of Smoothing Reactor and Ignitron Tube.


WAM2 (1960-64) : 10Nos. 2790 HP Mitsubishi  design and manufactured weighing 76Tonne, 25.24 T starting tractive effort and maximum speed of 112kmph with ? Nos. ?kW/725V, water cooled Ignitron Rectifier; Mitsubishi  MB 3045A – 745hp, 725V, 815 A, 1000rpm weighing 2200 kg; all motors working in parallel,  fully suspended force ventilated traction motor; Jeumont Transformer with 20 taps, B-B monomotor bogies, Jacquemin drive with pendular suspension and equalizer beams; Air brake for self and vacuum brake for trailing stock.


WAM3 (1964 ) : 2 Nos similar to WAM2 except with Silicon Rectifier type SF-OC20R 725V/2260kW, weight 2400kg along with blower motor. It may be noted that silicon rectifier was invented around 1955, with engineering use by 1958 and in India in 1964.


WAM series is suitable to mixed traffic, but when the requirement of higher tractive effort is there, exclusive WAG series was necessary particularly to work in heavy haul graded section of Chakradharpur Divison of South eastern Railway.


WAG1 (1963-66) : 2930 HP SNCF design and manufactured by Kraus-Maffei, Krupp, SFAC, La Brugeoise & Nivelle ( 50 cycle European Group), 85 Tonne, 30 T starting tractive effort and maximum speed of 85kmph,  4 Nos. Secheron A 268 Excitron Tube 510A/1250; Siemens/AEC/Alstom MG 1420A – ?hp, ?V, ? A, ?rpm weighing ? kg fully suspended force ventilated traction motor; Oerlikon Transformer BOT 3150 with 32 taps, B-B monomotor bogies, Jacquemin drive with pendular suspension and equalizer beams; Air brake for self and vacuum brake for trailing stock.


WAG2 (1964-65) : 3450 HP Hitachi/Toshiba/Mitsubishi make;  86 Tonne, 30 T starting tractive effort and maximum speed of 80kmph,  2 Nos. silicon Rectifier type AEV-48 2040A/2550kW; Hitachi Traction Motor EFCO HKK  – 1700hp, 1250V, 1080A, 695rpm weighing 5300 kg fully suspended force ventilated traction motor; Hitachi AF1 AMOC Transformer   with 32 taps, B-B monomotor bogies, Jacquemin drive with pendular suspension and equalizer beams; Air brake for self and vacuum brake for trailing stock.

WAG3(1965) : 3590 HP Henschel make 87 Tonne, 30 T starting tractive effort and maximum speed of 80kmph,  2 Nos. Silicon Rectifier GL 82220     1000A/1270;  AGEC  1580A – ?hp, 1270V, 1040 A, 680rpm weighing 5850 kg fully suspended force ventilated traction motor; Oerlikon Transformer BOT 3460 with 32 taps, B-B monomotor bogies, Jacquemin drive with pendular suspension and equalizer beams; Air brake for self and vacuum brake for trailing stock.


Contract on 50 cycle group was with transfer of technology and therefore CLW also manufactured 91 WAG1 and 186 WAG4 (Silicon Rectifier) locos during 1963-66 and 1966-71 respectively.



There were many problems associated with the working of BO-BO design bogie with fully suspended motor of WAG1&4 class of locomotive.  This has called upon Indian Railway Engineers to develop suitably designed locomotive to meet the specific requirement of heavy haul and gradient.  CO-CO bogie design with axle hung and nose-suspended motor of WDM2 loco was well established by that time and it was decided to suitably adopt the design and gave birth to WAM4 and WAG5 class of locomotive. WAG1&4 class of locomotive later on transferred from SER to SC and WR in the year 1980 for operation in plain territory.

This was the period of many happenings namely

1          Development of Air brake Electric locos for operation in newly electrified Waltair-Kirandul section during 1980-81 where trailing stock was equipped with Air brake system only and thus developed WAM4B initially and later on called WAG5B. Three locos in multiple called consist operation compulsorily with Dynamic and air brake were called for.

2          Vacuum Brake System was causing immense problems of delayed start of freight at yards as well as passenger trains at stations and it was decided to switch over to air brake system. WABCO system which was prevailing on WDM2 locos was adopted on Electric Locos.

WAM4manufactured initially were provided with flat roof fastened with number of fasteners. This design lapse has caused the biggest maintenance problem of water ingressing inside the locomotive leading burning equipment, rusting etc.

3          Alsthom make TAO659 was imported from France with technology transfer and provided on WAM4 class of locomotive. CLW started production of TAO traction motor from 1971 onwards. This motor gave immense problems and underwent many modifications initially in armature and later on in stator. It was mainly due to suspension arrangement not suitably designed.  This led to another technology transfer from Hitachi with provision of roller suspension bearing in lieu of plain sleeve suspension bearing used in TAO659. This motor was found to be highly successful and has helped Indian Railway Engineers to develop WAG7 (with high adhesion bogie) and WAP4 (flexi-coil bogie) class of locomotive, most successfully and met the challenge of high horse power and speed indigenously.

4          Thyristor was invented in 1958 and available as power device by 1960s. Tap Changer control for armature voltage was associated with many problems of flash over and also incidences of fire on locos, called for development of Thyristor control. A developmental order for conversion of 10 nos. WAG1 (20700-09) from tap changer control to Thyristor control was placed on ECIL/BARC, who were the technological giants at that time in India. The first locomotive was inaugurated in Feb 1980 at Electric Loco shed /Tatanagar. However, this finally ended an unsuccessful development.  A second effort was also made with BHEL to convert WAM4 loco into Thyristor control but again unsuccessful.

5.         Period of 1974-80 was the period of economic slowdown, labour unrest and therefore import of technology and equipment’s were restricted.

6.         It was learnt during the period that it is very difficult to select technology on the basis of proven and running in host country with limited test and trial. Technology selection was the most difficult assignment. Therefore, tenders were invited with the purpose of trying with not only one but many proven technologies of abroad. Finally WAG6A,B&C class of locomotive were imported from ASEA (6nos) and Hitachi ( 6nos each of CO-CO and BO-BO-BO design respectively) to undergo extensive triasl. Evaluations were done, but by that time power converter technology changed significantly with coming of GTO and IGBT. This development did not proceed further and now these locos are working in Waltair Kirandul section of Waltair Division and getting grounded one by one due to maintenance issues.

7          The end of this period saw the creation of the post of Member Electrical thus helping the process of decision making.

8          In case of derailment, if the derailed rolling stock infringes the other line, there is not sufficient time to protect the other line, and there are chances a train coming from other direction and colliding with the derailed coaches. There was a major disaster in the year 1980 which led to installation of flasher light on coaches so that the driver of the approaching train could be alerted. The flasher light operation made automatic in the year 1998 by sensing the drop of pressure.

9          ABB make air blast circuit breaker were provided called DJ or Dis-Jointer. There were large number of wearing and tearing parts and changed over the Vacuum Circuit Breaker introduced from…

10        Loco transformers were developed from 3460kVA capacity used initially on WAM4 locos to 3900kVA (WAG5) and thereafter by 5400kVA (WAG7) totally indigenously.

11        Indian Railways decided to go for air brake system for trailing stock. This was a gigantic job for conversion of entire fleet of existing locos into dual brake. WABCO design was suitably followed for the said conversion. It was also learnt that working of all the six traction motor in parallel improves redundancy and reliability of locomotive on line and therefore, dual brake conversion also associated with 6P conversion of locos.

12        Introduction of Flexi-coil bogie with double suspension and bolster for 140kmph & above in WAP1, 2 & 4 and high adhesion bogie for WAG7 class of locomotive.

13        Development of roller suspension bearing for axle hung arrangement of traction motor type TAO 659 called TAOCHI conversion i.e. conversion of TAO suspension similar to Hitachi.

14        Initial Head light was working on 32V AC with incandescent lamp fed by RTPR transformer. The head light was switching off when panto lowered or passing through neutral section. DC-DC converter with twin beam sealed headlight introduced. Water ingress was one of the maintenance issues causing frequent failure of flashover and bulb failure.

15.       Dynamic Brake has undergone many design changes write from the inception. The initial design was taken from WDM2 locos which underwent modification one by one as given below

  • WDM2 design taken from BHEL found problem of burning of grids due to ventilation issues as the panel was enclosed inside the locomotive.
  • Eaton Make DBR was installed on WAG6A class of locomotive and decided for use on CLW manufactured locos, but the issue of burning of grids continued.
  • It was then decided to provide fixed speed three phase ventilation motor using the spare capacity of spare capacity of Arno and Static Inverter.
  • Another design decided for mounting of resistor grid over roof which will provided natural ventilation. It was also found inadequate capacity
  • The present desing concept is to provide natural as well as forced ventilation on roof mounted DBR unit.


GTO and IGBT devices were developed successfully to control the voltage and frequency of input supply thus opening a gate-way for bringing three phase induction motor to work as Traction motor. It was only the power handling capability and switching frequency which The technologies were introduced for Locomotive and EMUs simultaneously through following tenders.

Post a Comment

Your email address will not be published. Required fields are marked *