The Loco Story :

Prototypes were imported from General Motors (# 20000 - 20009). Indigenous production started by Diesel Locomotive Works, Varanasi first in 2002.

These are the newer class of dedicated mainline diesel passenger locomotives. Transfer of technology from GM's GT46PAC models.

The locos are rated at 4000hp and use 3-phase AC traction motors with maximum speed of 160 kmph

The fabricated underframe has a rigid design. The bogies are GM's light-weight cast HTSC bogies similar to those of WDG4 locos but meant for passenger use.

The suspension is a two-stage suspension. They have an interesting Bo1-1Bo wheel arrangement.

The bogies are said to have a 'million mile' overhaul interval because of a reduction in the number of wearing surfaces.And usually scheduled for a 90 days return for maintenance.

Recent WDG4 units have GTO control of the traction motors.

The EM2000 onboard microprocessor system provides a flexible and expandable control system with complete self-analysis and unit history features.

WDP4B are modified versions having 6 traction motors with individual inverters, Co-Co bogie type, axle load of 20.2t, Gear Ratio 17:77, 4500 hp and the maximum tractive effort is 384.4kN with wider cabs & 150 kmph of top speed. Prodcution started on 2010. Traction control uses IGBTs instead of GTOs. Can be used as HOG.

WDP4D refers to a dual cab version of the WDP4/WDP4B design, intended to eliminate the problem of running long hood forward. The cabs have a slightly wider profile like WDP-4B, to improve visibility.

Technicalities :

Engines --- GM-EMD 16-710 G3B, 4000hp, with EMD 'G' turbocharger.

WW PGR governor. Unit fuel injection, centrifugal pump as with WDP-2, cooling and fan as in WDP-2.

Transmission --- Electric with TA-17-CA6A alternator, 900rpm, 2200V AC/3000V DC, 1600A AC, 2100A DC.

Loco weight --- 119 tonnes

Bogie type --- Bo1-1Bo fabricated cast HTSC bogies.

Tractive effort --- 27 tonnes at 32% adhesion.

Traction motorss --- Crompton, alternators by Kirloskar (in later versions). EM2000 onboard microprocessor.

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