Demagnetization conditions comparison for line-start permanent magnet synchronous motors

To avoid the demagnetization risk, the largest demagnetization magnetic field is needed to be accurately predicted. Larger demagnetization field may occur under the starting process, or the abnormal operation conditions including out of step, three-phase short circuit, open-phase and reclosing of a line-start permanent magnet synchronous motor (LSPMSM). According to the partial demagnetization unconsidered by the traditional method, the time-stepping finite element method is adopted to take the irreversible demagnetization effect of each permanent magnet element into account under the demagnetization conditions. By the method, the irreversible demagnetization situations and the influencing factors, such as load factor and inertia moment factor, are analyzed. The more serious operation factors under every demagnetization condition are gained. Through the comparison of the performances after demagnetization under different conditions, the most serious demagnetization is occurred in the heavy-load starting process.