Welcome to Engineering Master. This article is about the working of a diesel rail engine used in railways. Please read my article Is the working of diesel and electric locomotive same? before reading this for proper understanding…
Diesel rail engine, as we discussed earlier, uses diesel to power up the rail engine. There is an internal combustion engine (IC engine) inside the diesel locomotive which runs with diesel (fuel) and generates electricity. This IC engine is known as diesel engine.
Diesel engine is the main part where power is generated. Diesel engine is connected to Alternator which generates alternating current (AC). This electricity is also used to power the electrical appliance of train coach like light, fan, charging points, etc. This is one of the ways to power up the coach.
Alternator only supplies alternating current (AC). Traction motor earlier worked with direct current (DC), but in new engines it work with alternating current (AC). If engine’s traction motor works with DC, then DC is obtained directly from Rectifier. Rectifier changes AC from Alternator to DC. And if traction motor work with AC, then rectifier’s DC is changed to 3 phase AC by using Inverter.
If you refer the figure, then you must see that ultimately traction motor runs with AC only. And AC is also obtained from alternator, then why so many conversion? Why don’t we run the traction motor with alternating current (AC) of Alternator? We can’t do it because Alternator is connected with Diesel engine directly. So the current generated in Alternator is fluctuating. And if we run traction motor with fluctuating current, then it won’t work properly. So Inverter is used to get stable AC.