A Hybrid Demagnetization Performance Prediction Model for Halbach Array PMSM Under Symmetry Short Circuit Fault

This article focuses on analyzing and evaluating the demagnetization behavior of Halbach rotor permanent magnet synchronous machines. An indicator related to the dq-axis current namely I-dmag representing the severity of the demagnetization is proposed based on the analysis of a finite-element (FE) model. The influence of transient symmetrical short-circuit (SSC) current is considered during the evaluation of the magnets' magnetization status. Analysis based on the derived analytical solution proved that ignoring the magnetic saturation caused by the transient SSC current will cause significant inaccuracy in the calculation of I-dmag. To improve the calculation efficiency and accuracy, a hybrid model combining the equivalent circuit model, several FE cases, and an analytical mapping model is proposed. The procedures for building the hybrid model are elaborated and its accuracy is verified by time-stepping FE analysis. The proposed model can complete the calculation of one case within 20 s whereas conventional FE analysis typically takes over 10 min. Finally, the accuracy of the FE model is verified by experiments on a manufactured prototype. With this proposed model, both the worst demagnetization scenario over the entire operating range and the maximum acceptable PM temperature at a given speed can be identified. The derived temperature boundary will be used to guide the cooling design of the machine.