Fault Detection and Tolerant Capability of Parallel-Connected Permanent Magnet Machines Under Stator Turn Fault

This paper analyzes the influence of stator windings turn-to-turn fault on inverter-fed permanent magnet (PM) machines. By adding a secondary neutral point (NP) in stator windings, the turn fault detection and tolerant capability can all improve considering a small turn-to-turn short at an early stage. From the perspective on fault detection, the proposed windings with two NPs increase the equipment impedance per NP. Once a turn fault occurs, the fault-induced voltage harmonic magnitude increases. It results in a better signal-to-noise ratio for the fault detection. From the perspective on tolerant drive, the fault-induced circulating currents can flow across different phase coils in the windings with two NPs. Reduced effect on circulating currents in a faulty machine is achieved due to the current diversion. Turn fault induced additional losses are then decreased compared to conventional windings with only one NP. A 1-kW PM machine with two different windings is tested to verify the fault detection and tolerant performance.