Comparative Parameters Investigation of Composite Solid Rotor Applied to Line-Start Permanent-Magnet Synchronous Motors

Abstract

This paper presents a composite solid rotor applied to improve the starting and synchronization capabilities of the line-start permanent magnet synchronous motor (LSPMSM). The rotor is mainly composed of solid steels to employ their high starting torque. A squirrel cage and some air slots are designed to be added on the rotor surface. During the starting process, the cage carrying eddy currents constitutes a branch in parallel with that of the solid steel, and hence decreases the total rotor impedance. Meanwhile, the surface slots enlarge the eddy current area of the solid steel and further reduce the rotor resistance. All these rotor parameters turning smaller lead to a higher induction torque, and thus enhance the motor performances of starting and synchronization. A set of comparisons about rotor parameters, induction torques, and speed-time responses are implemented among the LSPMSMs with the composite solid rotor and other solid ones lacking cage or slots. Results of the comparisons validate the advantages of the cage slot attachment as well as the motor performance improvement by applying the composite solid rotor.