Thanks for all the replies, they are greatly adding to my understanding of the aircraft's electrical (and inertial reference) systems. I feel that I have at least a rudimentary understanding of the IDG's whereas before I only knew that they made 400hz 115v AC power at 90 kva and what the function of the switches on the overhead were.
To take the discussion in a different direction, can anyone elaborate on the power source for the 744 GE CF6-80C2 EEC's both before engine start and after engine start? I'm guessing it's like other airplanes I've flown: FADEC's were powered off standby/essential buses prior to about 10% N2, at which point a dedicated permanent magnet alternator connected to the accessory gearbox would take over.
Thanks for the continued responses, again they are very informative.
-RP8