The invention provides a generator (100, 400, 500). The generator includes at least one rotating member (202, 418, 518); at least one stationary member (204) arranged to define a gap (208, 424, 524) between a portion of the rotating member and a portion of the stationary member ), wherein the gap is configured to facilitate the transfer of a controllable magnetic flux therethrough; and a gap control system (200) comprising at least one gap measurement assembly (218, 220, 222, 428, 528), at least one power a transducer (232, 234, 236) and at least one controller (224) electronically connected to the measurement assembly and the transducer and configured to adjust the size of the gap by adjusting the magnetic flux .