Torque speed characteristic of polyphase permanent magnet motors with one phase fault

This paper analyzes the effect of the phase number on the fault tolerance of polyphase motors when an inverter supplies a PM motor with current and voltage limitations. The behavior of the motor depends on machine impedances and it is not possible to neglect their effect for the estimation of the torque-speed characteristic. We present an optimization-based modeling method to analyze the torque-speed characteristic of several drive configurations and fault conditions. It is shown that higher number of phases increases the performance of the drive with one phase fault and decreases the overrating necessary for fault tolerance. The results show that the inverter voltage limitation reduces the system performance with one phase fault at high speed compared to previous simulation methods that neglect the voltage limitation.