Calculation of magnets´ average operating point during the starting process of line-start permanent magnet synchronous motor

During the starting process of line-start permanent magnet synchronous motor (LSPMSM), the strength of demagnetization field produced by currents in stator windings and rotor bars varies with time, so does the operating point of permanent magnets. Existing studies mostly adopt finite element method (FEM) to study the variation of magnets´ operating point in LSPMSM during the starting process. But the calculation by FEM is time consuming, thus it is not suitable for fast calculation at the design stage. Based on MATLAB/Simulink, this paper establishes the analytical model to calculate the variation of magnets´ average operating point during the starting process of LSPMSM, by combining dynamic mathematical model and magnetic circuit model of LSPMSM. The calculation result is compared with finite element calculation. Results show that the established model can accurately calculate magnets´ average operating point when the severest demagnetization field of LSPMSM during the starting process occurs as well as magnets´ average operating point when LSPMSM operates at steady state, and it can be used for the fast design of LSPMSM.