Modeling and detection of demagnetization fault in permanent magnet vernier machine using flexible magnetic equivalent circuit method

In this paper, an analytical model is proposed for evaluating electromagnetic performances of permanent magnet vernier machines (PMVMs) under healthy and faulty conditions. The proposed model employs flexible magnetic equivalent circuit (MEC) method, which its accuracy can be selected by tunable parameters. The model is capable of considering the influence of saturation effect, skewed slots, slot leakage fluxes, and various winding arrangements for the machines with desired properties. First, the proposed model is used to predict the no-load performance of machine at healthy condition. Then, the machine loading behaviors under healthy and demagnetization fault conditions are analyzed by the MEC model. Moreover, the results of the proposed model are compared and validated with those of 2-D finite element method (FEM) and 3-D FEM. Eventually, a specific pattern is extracted from the stator current spectrum to detect the demagnetization fault.