48V Starter-Generator Induction Machine with Pole Changing Windings

An electronic pole changing winding induction machine with 8 and 4 poles for a 48V starter-generator application is studied in this paper. Starter-generators require high torque capability for short durations at low speed for cranking and a wide flux weakening region for regeneration with high torque density so that the machine may be integrated into a drive train with minimum change to the existing system. In this paper, it is shown that when the pole changing windings are used, the axial length of the machine can be reduced compared to the baseline induction machine design resulting in a more compact machine. The effect of shorter stack length and pole changing windings on the performance of the induction machine are studied. Efficiency, loss and power factor maps are calculated with analytical and finite element methods to compare the performance of the pole changing winding induction machine with a baseline design under different operating conditions.