Variant of WAP-1 with Hitachi H5 15250 motors (built by CLW), built in 1994 to RDSO specifications. The need to run longer passenger trains (24 to 26 coaches as against the 19-coach capacity of the WAP-1 / WAP-3 locos), and also to eliminate the need for bankers in graded sections (e.g., the busy Itarsi-Nagpur section) led RDSO to consider an upgraded design of the WAP-1 loco and the WAP-4 loco design was published in November 1993. Indigenously designed, higher power rated silicon rectifiers and indigenously-designed 5400kVA transformer. Locomotive reliability is also increased by the use of Hitachi traction motors. Air brakes for loco and train. Different underframe design to handle larger buffing loads. Cast bogie, Flexicoil Mark 1 design. Weight kept to 112t by the use of aluminium plates, thinner underframe, and reducing some components such as sanders. Motors grouped in 6P combination; weak field operation possible.
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New versions of these with twin-beam headlights, speed recorders and some changes to the control electronics have been rolling out recently [7/00]. WAP-4E are most likely just regular WAP-4 locos from the Vadodara shed. The 'E' suffix is thought to come from the short-lived RDSO directive to denote all air-braked locos and is redundant with the WAP-4 locos (e.g., WAP-1E). There is speculation that some of these locomotives may have some additional features such as an electronic sensor for detecting loss of pressure in brake pipes (hence, sometimes the 'E' suffix is explained as 'electronic', although this seems unlikely). More recently [1/05] many of these have been fitted with train-parting / pressure loss alarms, and data recorders for speed, energy consumption, etc. All the new ones have roof mounted twin beam headlights, square WAP-5 type windscreens and a digital notch repeater along with a better layout and good seats for the drivers. Some [12/04] even have windshield washers. A few were provided with signalling lamps on the sides but this does not have seem to have continued with the newer units.