When the aircraft is flying in normal conditions, the engines will both be operating. The engines of course provide thrust to propel the aircraft forward and allow the wings to create lift – but they also have many other essential functions.Read more
One of these functions is that they are the main source of power during a flight and while one engine can electrically power the aircraft, it is normally the case that both will be doing this.
We generate AC (Alternating Current) with a generator called an Integrated Driven Generator or IDG. This is a sophisticated bit of equipment as it generates 400Hz (cycles per second) and 115 Volts AC.
There is one IDG per engine and it is installed on the associated engine gearbox. This means that when the engine operates, the gearbox is powered, and it rotates.
We use a little of the torque from the gearbox to operate the generator. Of course, the engine speed will increase, and decrease based on many factors such as altitude or if we are in a climb of decent profile.
So now let us consider the name of the generator – integrated drive generator. Why integrated?
Well, it combines what historically in aircraft was 2 separate components.
Constant Speed Drive (CSD) – which maintains 400 Hz regardless of engine speed when it operates.
The Generator itself, when rotated it will provide 115 V AC and 400 Hz 3 phase power.
Each IDG is controlled and monitored by its corresponding Generator Control Unit (GCU) and this maintains that the power generated is safe and not going to damage the aircraft.
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