Optimizing an Interior-Permanent-Magnet Tooth-Coil-Winding Traction Motor for its Entire Operating Range

Abstract

Design and optimization of an interior-permanent magnet motor (IPM) with tooth-coil-windings (TCWs) for traction motors are studied. Main goals are to deliver high torque and low torque ripple in the entire range of operation with lowest possible magnet usage. Design of an IPM-TCW motor with acceptable torque ripple in its entire operation range is challenging due to several reasons such as variation of harmonics of stator and rotor current linkages with saturation, slotting effects, and unity winding factor for all harmonics (for 12 slot 8 pole). Moreover, torque ripple varies based on the requested current angle and current density. In this study, an effective optimization method is proposed to reach an acceptable average torque and torque ripple in the whole range of operation. To further decrease the torque ripple utilization of notches on the rotor surface and semi magnetic wedges in the stator are proposed and compared with rotor skewing as an alternative. A model of IPM traction motors, with single V positioned magnets for an electric motorcycle is implemented and investigated. The Optimized machine has a power rating of 6 kW with maximum speed of 10,000 r/min operating speed with a 48 V battery. Finite element method is utilized to optimize the geometry of the IPM motor.