Study on Pole-changing Starting Scheme for Line-start Permanent Magnet Synchronous Motor

Through Pole-changing starting strategy, line-start permanent magnet synchronous motor can obtain higher starting capacity by effectively suppressing the braking torque and pulsating torque during starting process. In this paper, the pole-changing starting scheme, including the design principles of the pole changing stator winding and the determination of pole numbers for minor-pole winding, are studied. The 8-pole line-start permanent magnet synchronous motor is taken as example, the corresponding 2/8, 4/8, 6/8 pole changing windings when starting with 2-, 4-, 6-pole modes are designed based on slot number phase diagram method and slot electromotive force star diagram. And through comparison, the reasonable pole-changing starting scheme is determined. Then, based on finite element method, a 30kW, 6/8 pole changing line-start permanent magnet synchronous motor is designed, the armature magnetic field and the fundamental air gap magnetic density under 6-pole and 8-pole states are calculated. Finally, a prototype is manufactured and tested.