Fault detection and tolerant capability of parallel connected permanent magnet machines under stator turn fault

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