Analysis and Diagnosis of Irreversible Demagnetization Fault of Surface-Mounted PM Synchronous Motor

This paper introduces a novel method to detect irreversible demagnetization fault (IDF) using the harmonic characteristics of the coil back electromotive force (BEMF) for surface-mounted permanent magnet (PM) synchronous motor. Firstly, an analytical method of IDF based on the subdomain method and PM subdivision model is proposed, which can simulate uniform demagnetization and partial demagnetization in tiny areas on a single PM. The model is verified by finite element analysis, which has high accuracy and computational efficiency. On this basis, the harmonic characteristics of the phase and coil BEMF of the integer-slot motor and fractional-slot motor under three IDF states are investigated. Finally, a diagnosis technique of IDF based on the harmonic characteristics of coil BEMF is presented.