Single-phase fault diagnosis for five-phase permanent magnet synchronous motors based on neutral voltage observation

Neutral voltage (NV) reflects the unbalanced condition of a five-phase permanent magnet synchronous motor (PMSM). Thus, it can be used to screen out the open-switch, open-phase, and inter-turn faults of a single phase, with a low rate of misdiagnosis. However, because there is no neutral point lead for most electric drives, the measurement of NV is difficult. To this end, an NV observation method is proposed in this paper by exploiting phase currents and reference pole voltages. This method can be regarded as a kind of multi-sensor information fusion technology. On this basis, a lock-in amplifier technique is further presented to calculate the frequency spectrum from the re-constructed NV, which achieves accurate classification of the stated single-phase faults. Finally, experimental results confirm the validity of the presented method in terms of fast and accurate location determination of open-switch, open-phase, and inter-turn short-circuit faults.