High phase number induction motor drives for battery applications

A demonstrator drive has been designed, built and tested and the results show that high phase number induction drives are well suited for battery powered applications. Their reduced current per phase mitigates common problems of three-phase induction motors in battery drives. This paper has confirmed that squarewave excitation leads to a significant reduction of inverter losses compared to conventional PWM and how the adverse effects of squarewave excitation on motor performance can be mitigated by increasing number of motor phases. The complexity of a six-phase battery drive is only marginally increased compared to a three-phase battery drive because no paralleling of switching devices is required, therefore keeping the total number of switching devices the same. The combination of low inverter losses, lower phase currents, and excellent performance over a wide speed and power range make high phase number induction motors attractive for low voltage battery powered drives