WAP 4

The WAP 4 is a class of 25 KV AC electric locomotive used in Indian Railways for passenger trains.

The locomotive was developed after a previous classes WAP 1, WAP 2 and WAP 3 were found inadequate to haul the longer and heavier express trains that were becoming the mainstay of the Indian Railways network. It was introduced in 1994, with a similar bodyshell to the WAP-1 class, but with Hitachi traction motors. Electrical System are traditional AC loco type tap changer, driving six traction motors arranged in Co Co and 6P Configuration. This locomotive has proved to be highly successful, with over 750 units in service. Newer examples were fitted with WAP 5 style windshields, microprocessor-controlled diagnostics, static converter units (instead of Arno) and roof-mounted DBRs. The locomotive can be seen in service across the electrified network of Indian Railways and is homed at 14 different sheds (depots).

Production ceased On 2nd December 2015 with the rolling out of WAP 4 #25051 from CLW Production line. WAP 4 #25051 is the last DC traction motor using locomotive ever produced in India, making way for more advanced 3 Phase AC locomotives to be produced.

History
WAP 4 started its Life as a variant of WAP 1 with Hitachi H5 15250 motors (built by CLW, Used only on goods locomotives until then), 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 locomotives), and also to eliminate the need for bankers in graded sections (e.g., the busy Itarsi-Nagpur section in CR) led RDSO to consider an upgraded design of the WAP-1 loco and the WAP-4 locomotive design was published in November 1993.

Indigenously designed, higher power rated silicon rectifiers and indegenously-designed 5400kVA transformer. Locomotive reliability was increased by the use of Hitachi traction motors. Air brakes were provided for loco and train. Unlike WAP 1, WAP 4 featured different underframe design to handle larger buffing loads. Bogies used were Flexicoil Mark I. Weight was kept capped at 112t by the generous use of Aluminium, thinner under frame, and reducing the number of some components such as sanders. Traction Motors were grouped in 6P combination; weak field operation is possible.

New versions of WAP 4 came with twin-beam headlights, speed recorders and some changes to the control electronics.

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. More recent Units 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 Units 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.

Service
The WAP 4 was developed to counter the shortcomings of its Predecessors WAP 1 and WAP 3. Initial 12 units Were WAP 1s which were converted to WAP 4 during 1994. Massively better performance and reliability prompted Railways to Mass Produce the locomotive.

WAP 4 quickly took over the AC Electrified Railway Network and became the most common passenger Electric locomotive, remaining so until WAP 7 overtook WAP 4 in production Numbers. All Units Sport The WAP 4 livery; Red body with narrow Yellow Band with occasional ones painted in the ICF rajdhani Livery. Performance figures were A massive improvement over WAP 1 and WAP 3. The locomotive has a restricted Top speed of 140 km/h and is said to have been tested upto 169.5 km/h by CLW, making it one of the fastest Locomotive in IR's Roster.

WAP 4 are still used for hauling Premium Trains and Expresses alike but railways plan to replace the fleet with the much more advanced WAP 5 and WAP 7 fleet.