ATPL - The function of a constant speed drive (CSD) in an AC generating system is to:

Question id 546 - Aircraft General Knowledge - Airframe, Systems, Powerplant - ATPL - Airline Transport Pilot license

Directly Maintain A Constant Proportion Between The Rpm Of An Engine And A Generator.

Vary generator rpm in order to compensate for various AC loads.

Vary the engine rpm (within limits) to compensate for various AC loads.

Drive the generator at a constant speed.