The effect of stator winding configuration on the performance of brushless doubly-fed machines in adjustable speed drives

Recent developments in power electronic converters have renewed interest in the doubly fed connection of the self-cascaded or concatenated induction machine. These brushless doubly fed machines (BDFMs) utilize die-cast cage rotors and have the potential to provide economical alternatives to regular induction machines in the areas of variable-speed generation, pumped storage, and adjustable-speed drives. Working laboratory prototypes have been constructed to provide both a proof-of-concept and a baseline for design development. Improvements in machine design, based on alternatives for the stator winding, are discussed. Working within the framework set by stator geometry and the cage-rotor design of the proof-of-concept machine, the authors investigate the effects of various design strategies, such as varying the coil span, unconventional winding distribution, providing alternative connections, of incorporating two electrically isolated stator windings. The results derived from a detailed design model are presented.<>