Analysis on the Starting and Synchronization Capabilities for a Novel 6/8 Pole Changing Line-Start Permanent Magnet Synchronous Motor

摘要

Line-start permanent magnet synchronous motor (LSPMSM) has been widely used in applications such as pumps, fans and compressors for its high torque and power density, efficiency and power factor [1]-[2]. However, it suffers from the poor starting and synchronization capabilities, and always a compromise between the starting and synchronization capabilities is adopted because of the conflict with each other [3]-[4]. So far, several different rotor configurations, such as squirrel-cage rotor, solid rotor, slotted solid rotor, two-part rotor geometry and so on [5]-[7], and different magnet, cage bars shapes [8]-[9], were presented and discussed to improve the starting and synchronization capabilities. But the starting capability cannot get fundamentally improved for the existence of the braking and pulsating torques. In [10]-[12], the pole changing method was presented, and the drawbacks of PMSM got overcame. However, more switches were used, and the reliability was reduced for the proposed 2/4 pole changing winding. In addition, the turn numbers cannot be adjusted to balance the starting and running performance. In this paper, a 6/8 pole changing LSPMSM is designed based on the novel 6/8 pole changing stator winding. As the different pole numbers between stator winding and rotor PMs during 6-pole starting process, the inherent braking torque and pulsating torque for conventional LSPMSM can get effectively eliminated, and the starting capability can be fundamentally improved. Furthermore, as the effective improvement of the starting capability, the rotor resistance can be optimized to be smaller to improve the synchronization capability simultaneously.