Open-Circuit Fault Diagnosis of Three-Phase Permanent Magnet Machine Utilizing Normalized Flux-Producing Current

In this paper, an open-circuit fault diagnostic method is proposed for three-phase permanent magnet machines. By individually applying inverse coordination transformation tod- andq-axis currents, per-phase current can be decomposed into flux- and torque-producing currents. Their post-fault behaviors are found to be highly related with the fault types and locations. Hence, the normalized flux-producing current can be used as a single fault index to detect and identify both open-switch and open-phase faults. Since the established fault index is close to zero, the proposed fault diagnostic method is naturally robust to load/speed variations. In addition, a low decision threshold can be set to reduce fault diagnostic time. The robustness and effectiveness of the proposed method are verified by the experiments on one prototype.