Study on the Winding Switching Process of Pole Changing LSPMSM

Through adopting pole changing starting method, the starting capability of the line start permanent magnet synchronous motor (LSPMSM) can be significantly improved. However, the switching of the winding is inevitable and crucial. Adverse switching will produce large impulse current and torque, which will have adverse effects on the power grid, motor, permanent magnet and load, and also affect the subsequent pull-in synchronization process. In this paper, based on a 6/8 pole changing LSPMSM, the dynamic winding switching process is studied. The effects of the switching speed and switching phase difference between the 8-pole winding and the applied voltage on the speed, current, electromagnetic torque and the demagnetization of permanent magnet during winding switching process are analyzed, respectively. The results show that the switching phase difference (or voltage difference) should be as small as possible to reduce the impact on motor. Subsequently, a switching control strategy with small impact on power grid, motor and load, no irreversible demagnetizing of permanent magnet and favorable to pull in synchronization is proposed.