The whole blasted fort is acting like the squirrel cage in an induction motor!
For motor-generators where alternating current is used, the induction motor is generally employed.
This is one of the first models used by Mr. Tesla as an induction motor and rotating transformer.
Another prominent exhibit was a model illustrated at C which is a two-phase motor, as well as an induction motor and transformer.
The coil represents the stationary part, the stator (Fig. 445) and the cup the rotating part, the rotor, of an induction motor.