Indian Railways Diesel Locomotive: APU fitted WDM3A - A day of a locomotive

A day of a locomotive - Various duties performed by a diesel locomotive of Indian Railways, captured at Jalandhar City Junction, Punjab, India.

AUXILIARY POWER UNIT (APU) is actually an alternative source of power for a diesel locomotive. APU consist of a small naturally aspirated 3-cylinder 4 stroke diesel engine connected to an alternator and a small compressor. It is installed in the short hood of the locomotive.

Auxiliary Power Unit (APU) is a unit consist of a three main components:

1. Naturally aspirated 3-cylinder 4-stroke diesel engine - to drive compressor and alternator simultaneously
2. Air compressor - to maintain Air Brake pressure
3. Alternator - to charge the main engine starting batteries

When a diesel locomotive idles, it actually performs two functions:
1. Prevents the batteries from getting discharged
2. Maintains the air brake's air pressure of the rake (if attached to some rake)

THIS IS WHY THE DIESEL LOCOMOTIVES ARE SELDOM TURNED OFF, but this results in massive wastage of fuel.

In order to get rid of this problem, APU is equipped in the diesel locomotives which performs these two functions, i.e. the main 16 cylinder diesel engine inside the locomotive is turned off and the small diesel engine of the APU is turned on.
Main function of APU are:
1. To maintain the Air brake pressure more than 1.5 Kg/Cm² (approx)
2. To keep the main engine starting battery in fully charged condition
This is how the whole system works.

Normally, diesel locomotives consumes about 25 L/hr diesel whereas APU consumes only 5 L/hr diesel.

#AbhinavLHB #WDM3A #Jalandhar #Punjab

[nilanjanmajumdar]

Well, it's 16642R. And thanks for the useful information provided in the video description :)