I rememebr the cables need to feed juice to the Ecko 190 radar. Thick as my arm! And the rotary inverters on the Jet Provost accounted for about 30% of it's AUW!
Looking back to aviation electronics history, the Handly Page Victor Mk1 of the early 1950s had 'Alternators' producing 208V frequency wild AC. Rotary inverters then provided frequency stable AC at 400 and 1600hz. As the aircraft had electric powered flying controls, a backup was needed. So it had ten (yes, ten!) 28V batteries! Hardly a weight efficient solution, but the best the age could produce.
Then in the late 50s, the Victor Mk2 came along with CSDU driven generators which produced 200v 3 phase 400hz power with backups of an APU and two ram air turbines. This system was very similar to the VC10's, (which I flew later) and the VC10's was almost identical to the 747's which didn't change much on the introduction of the -400.
I seem to remeber the Jetstream 200 had both AC generators and DC generators. Not many people copied that system!
The torque switch: If I remember correctly, it was on a rotary inverter and was held open by the current induced by the rotaion of the generator part of the inverter. If the rpm dropped, the switch closed and put on a warning light on the flight deck to tell you the AC supplies to you instruments were suspect. As always, I'm open to the inevitable correction on that piece of information.