Indian locomotive class WAP-4


The WAP-4 is a class of passenger hauling electric locomotive used in Indian Railways.
The locomotive was developed after its predecessor, the WAP-1, was found inadequate to haul the longer, heavier express trains that were becoming the mainstay of the Indian Railways network. It was introduced in 1994, with a similar body-shell to the WAP-1 class, but with Hitachi traction motors. The electrical systems are traditional direct-current loco type tap changers, driving six traction motors arranged in Co-Co fashion. The locomotive has proved to be highly successful, with more than 750 units in service. Newer examples have been fitted with microprocessor-controlled diagnostics, static converter units and roof-mounted dynamic brakes. The locomotive can be seen in service across the entire electrified network of Indian Railways and is homed at 14 locomotive sheds.
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.

Design

The loco has a streamlined twin cab carbody design, with twin beam, top-mounted headlamps. The first 150 or so units had the headlamp mounted at waist level, with the lights being mounted in a protruding nacelle. Some earlier locos, especially from the Erode loco shed have the headlamps placed on the top. Later on the headlamps were placed in a recessed nacelle, and from road #22579 onward, the headlamps were moved to the top.
The loco is equipped with digital notch repeaters. Newer locos also feature larger windshields, more spacious driver cabin with bucket seats and ergonomic controls. The control panel has a mix of digital and analog displays in newer units while the older units were mostly analog.
Original units weighed 120 tonnes, which was later brought down to 112 tonnes through the usage of lighter material.
Some of the WAP-1 and WAP-3 and all the WAP-6 units were rebuilt to WAP-4 specifications after replacing the bogies & electricals.
It has different underframe for handling larger buffing loads. Some units are fitted with speed recorders and some changes to control electronics. Some units also have data recorders for energy consumption. Some are even fitted with windshield washers and rearview mirrors. Few were provided with signalling lamps which were subsequently removed.
Technical variants include WAP-4E which are probably fitted with electronic sensors for sensing pipe pressure loss.
The Hitachi traction motors are the ones used on freight engines. It was a challenge to put these in a passenger engine due to weight constraints. So the transformer is aluminum foil-wound and aluminum chequered plates are used for reducing the weight.
415 volts, three-phase, 50 Hz power supply is used to drive various auxiliary motors like Traction motor blowers Transformer radiater blower Transformer oil pump Smoothing Reactor Blowers Silicon Rectifier Blowers Battery charger. The three-phase, 415 volt supply is obtained from the single phase supply by Arno converter or static converter.
Indian railways has installed microprocessor based fault diagnostic system and Vigilance Control Device for the enhancement of safety and reliability of electric Locomotives. Some of the newly manufactured WAP-4 locomotives also have air conditioning system for the loco pilot.

Performance

If the average weight of ICF coach is 55 tonnes then it can haul the following capacity in tonnes:
GradientStart20 km/h40 km/h60 km/h70 km/h80 km/h90 km/h100 km/h110 km/h120 km/h130 km/h140 km/h150 km/h160 km/h
Level1500+1500+1500+1500+1500+1500+1500+1500+1500+1500+1500+1155805570
1 in 5001500+1500+1500+1500+1500+1500+1500+1500+1500+1500+1105805565400
1 in 2001500+1500+1500+1500+1500+1500+1500+132012301035730535375260
1 in 1501500+1500+1500+1500+1500+1500+140510901020860610445310215
1 in 1001500+157014901405136511951020795750635445320220145
1 in 5011607707507207106255304103903252201509045

Technical specifications

Gear Ratio58:23
Transformer5400 kVA, 32 taps
Transformer coolingForced oil with Forced Air
Transformer InsulationA
PantographsTwo Stone India AM-12.
RectifiersTwo silicon rectifiers
Rectifier CoolingForced air
Current Ratings1300 A for 2 min, 1100 A for 10 min, 960 A for 60 min, 900 A continuous
Drive arrangementGear pinion
Number of sandboxes4
2 headlights90 W, 24 V
Lead acid battery10 Batteries each of 11 V, 75 Ah Capacity.
Arno Converter1420 rpm
2 Elgi Compressors1000 l/minute at 7.5 kg/cm2.
2 compressor motors3 phase 12.5 hp and 380 V
2 SF India Ltd. Traction motor blowersMLBR-42.5-144 type
2 Siemens Traction motor blower motors22 kW, 415 V, 50 A and 2820 rpm
2 SF India Ltd. Smoothing Reactor BlowerPFTA-50, ARR6 type
Traction Motor SuspensionAxle-hung, nose suspended
Traction motor weight3650 kg
Armature temperature rise90 °C
Field temperature rise70 °C
Commutator temperature rise85 °C
Armature coil resistance at 110 °C0.0126 ohms
Field coil resistance at 110 °C0.0117 ohms
Commutator coil resistance at 110 °C0.089 ohms
Traction motor continuous rating675 kW, 750 V, 900 A and 895 rpm
Traction motor 1 hour rating1030 hp, 750 V and 877 rpm
Traction Motor air gap main place6.35 mm
Traction motor air gap inter-pole10 mm
Traction motor6 P
2 SF India Ltd. silicon rectifier blower3100–3200 m/hr
2 Rectifier blower motor22 kW, 415 V, 8 A, 2860 rpm and 60 kg
Oil cooler blower motor30 hp, 380 V, 43 A and 1450 rpm
BEST and Co. Pvt. Ltd. Transformer Oil Pump750 l/minute
Oil pump motor3.3 kW, 415 V, 6.6 A and 2865 rpm
SL-30 type smoothing reactor1250 V and 1350 A.
Smoothing reactor resistance at 110 °C0.00718 ohms
Notches32

Image Gallery

Locomotive sheds