A generator apparatus comprises a deicing circuit. The deicing circuit is operable during a time when a main generator rotor is not being rotated by a generator shaft. The deicing circuit includes a first power source for energizing a plurality of exciter field windings with alternating input current to induce an exciter output current in a plurality of exciter armature windings. The exciter output current is provided to main generator rotor windings for producing resistance heating around an air gap separating the main generator rotor from a main generator stator.