Analysis of Zero Sequence Current in an Open Winding Permanent Magnet Synchronous Machine Under Rotor Magnet Fault Condition

This paper investigates the partial demagnetization effect on zero-sequence current for fractional slot concentrated open winding permanent magnet synchronous machine. This analysis is crucial for developing fault tolerant control strategies, especially under the condition of rotor magnet fault. It has been observed that the zero-sequence current of the open-winding system is accompanied by low-frequency harmonics in addition to the dominant third harmonic current due to the partial demagnetization effect. These subharmonic and inter-harmonic components will lead to additional torque ripple and reduce the system efficiency. However, the order of these harmonics is influenced by the number of slots and poles. Both traditional and modular concentrated winding configurations have been studied in this paper. The analytical findings are verified by the finite element method and experiment.