Demagnetization Analysis of Permanent Magnet Synchronous Machines under Short Circuit Fault

Sudden symmetrical short circuit is a serious fault when the entire demagnetization or partial demagnetization of permanent magnet can occur. The aim of this paper is to analyze the demagnetization phenomenon of permanent magnet synchronous machines (PMSM) based on FEM and analytic method. Firstly, the transient FEM is utilized to analyze the demagnetization operating point of permanent magnet when symmetrical short circuit occurs. The computed time evolution of the maximum partial demagnetization operating point is derived. Secondly, the synthesized magnetomotive force (MMF) of the short circuit current is analyzed by analytical method. Through the analysis some characters are obtained. At last several factors that affect the demagnetization operating point are summarized and several measures are put forward to improve the max demagnetization operating point of permanent magnet.