Indian locomotive class WAP-4

The Indian locomotive class WAP-4 is a class of 25 kV AC electric locomotives that was developed in 1993 by Chittaranjan Locomotive Works for Indian Railways. The model name stands for broad gauge (W), AC Current (A), Passenger traffic (P) engine, 4th generation (4). They entered service in late 1994. A total of 778 WAP-4 were built at CLW between 1993 and 2015, which made them the most numerous class of mainline electric passenger locomotive until the WAP-7. The locomotive was developed after its predecessor, the WAP-1, was found inadequate to haul the longer, heavier express trains (24-26 coaches) that were becoming the mainstay of the Indian Railways network.

WAP-4
A Vadodara based WAP-4E running light
Type and origin Power type Electric Builder Chittaranjan Locomotive Works, West Bengal, India Build date 1993 till 2 December 2015 Total produced 778 as of August 2016 (Production Ceased)
Specifications Configuration: ​  • AAR C-C  • UIC Co'-Co' Gauge 5 ft 6 in (1,676 mm) Bogies Co-Co Flexicoil Mark 90 cast bogies; primary and secondary wheel springs with bolsters Wheel diameter New:1,092 mm (3 ft 7 in) Half worn: 1,055 mm (3 ft 5 1⁄2 in) Full worn: 1,016 mm (3 ft 4 in) Length 18.794 m (61 ft 7 29⁄32 in) Width 3.179 m (10 ft 5 5⁄32 in) Height 4.272 m (14 ft 3⁄16 in) Axle load 18,800 kg (41,400 lb) Loco weight 112,800 kg (248,700 lb) Electric system/s 25 kV 50 Hz AC Overhead Current pickup(s) pantograph Traction motors Hitachi HS15250 Loco brake Air Train brakes Air Safety systems Slip control, Over voltage relay, Main overload relay, Earth Fault Relay, Low Pressure Governor, Brake Cylinder Cutoff Valve, Train parting alarms and No OHE volt relay
Performance figures Maximum speed 140 km/h (87 mph) Power output Continuous: 5,050 hp (3,766 kW) Tractive effort Starting : 30,800 kgf (302 kN; 68,000 lbf)
Career Operators Indian Railways Numbers 22061 and from 22201-22399, 22500-22999 & 25000-25051 Locale All over India Disposition Active

The WAP-4 is one of the most successful locomotives of Indian Railways serving both passenger and freight trains for over 26 years. This class provided the basic design for other locomotives like the WAP-6 . Despite the introduction of more modern types of locomotives like WAP-7, a significant number are still in use, both in mainline duties. Production of this class was halted in December 2015 with locomotive number 25051 being the last unit to be rolled out of Chittaranjan Locomotive Works. As of January 2021, all locomotives except those lost in accidents still retain "operational status" on the mainline as WAP-4, with further examples having been converted back from WAP-6. Recently as per directive received from Railway Board [RB] all the loco sheds holding WAP-4 type locomotive have started "Mu" [Multiple Unit] operations. This configuration of Mu WAP-4 locos are being used to haul medium tonnage faster freight trains across IR.