On-line stator turn fault detection for inverter-fed electric machines using neutral point voltage differences

This paper proposes a stator turn-to-turn fault detection for inverter-fed electric machines using the voltage difference between two neutral points (NP´s). By designing machine Y-connected windings with a secondary neutral point (NP), a voltage difference between two NP´s appears once a turn fault occurs. Because this fault signal is induced by the voltage difference between two independent windings, only the turn fault reflected signal is resultant. It leads to an important improvement on the fault detection of standard electric machines since NP voltage difference is immune to the influence of saliency and saturation. In addition, the load and speed affect the signal level and frequency but not the diagnostic accuracy. It is possible to monitor a minor turn fault for the operation at zero and very low speed. A 200-W induction machine with designed two independent Y-connected windings is used for the experimental evaluation.