Torque Ripple Suppression Under Open-Phase Fault Conditions in a Five-Phase Induction Motor With Harmonic Injection

This article has made a study of the torque ripple suppression and torque capability maximization of a five-phase induction motor under open-phase fault conditions. The torque ripples are caused by the couplings between spatial harmonic fields after an open-phase fault in the motor. In order to assess the degree of coupling, multiple space vectors are introduced, which can be mapped onto different spatial harmonic planes. The current space vector components that cause torque ripples are eliminated for the goal of torque ripple suppression in the proposed strategies. Meanwhile, both the torque capability and the torque ripple after an open-phase fault need to be considered. When the phase current is limited to the rated value, the motor cannot simultaneously produce the maximum output torque and the minimum torque ripple. Hence, several postfault control strategies for different levels of torque capability and torque ripple have been proposed to meet the application requirements. Furthermore, postfault current space vectors have been optimized in the case of single- and two-phase faults. Finally, tests have been conducted on a five-phase prototype induction motor to verify the strategies proposed in this article.