Design of a Spoke Type PMSM With SMC Stator Core for Traction Applications

Abstract

This article presents four different slot/pole configurations to select the best slot/pole for a traction application with a wide speed range. The electromagnetic performances are improved for the selected slot/pole configuration. This paper presents a modified spoke type rotor that significantly reduces the torque ripple, back electromagnetic force (EMF) harmonics, and cogging torque from conventional spoke type designs. The effectiveness of the modified spoke type rotor is proved with state-of-the-art designs such as Toyota Prius and Honda Accord motors. Along with the modified spoke type rotor it focuses on a segmented soft magnetic composite (SMC) stator core to improve the copper fill factor and improve torque density by reducing the tooth length to allow additional space for the end windings within the stack length of the motor. A comparison between the laminated steel stator and SMC stator is presented. The laminated motor is capable of producing higher torque than the SMC motor when both machines are designed to operate with the same temperature, though the torque density in terms of volume of SMC motor is higher than the laminated motor. In all cases, the machines are designed to fit into the same frame. A cost comparison has been presented between the SMC and laminated motors, which proves that the SMC motors can be manufactured much cheaper than the laminated motors. Also, SMC stator design presents axial magnet segmentation, optimal flux weakening, thermal analysis, stator stress analysis due to electromagnetic forces, and a rotor mechanical stress analysis.