Design Optimization of an Interior Permanent Magnet Motor with Directly Liquid Cooled Tooth Coil Windings for Traction Application

Abstract

This paper presents design and optimization of an interior-permanent magnet traction motor (IPM) with directly liquid cooled tooth-coil-windings (DLCTCWs). The main goals are to deliver high torque and low torque ripple in the entire range of operations. Direct liquid cooling of windings ensures operation of the motor at a current density of $\mathbf{2 5} \mathbf{A} / \mathbf{m m}^{\mathbf{2}}$. The design of an IPM-DLCTCWs motor that maintains acceptable torque ripple across its entire operating range presents significant challenges. These arise from factors such as variations in the harmonics of stator and rotor current linkages due to saturation, slotting effects, and the presence of a unity winding factor for all harmonics in a 12-slot, 8-pole configuration. Moreover, torque ripple varies based on the applied current vector angle and current density. In this study, an effective optimization method is proposed to reach an acceptable average torque and torque ripple based on continuous and peak current densities. To further decrease the torque ripple, rotor skew is implemented. A model of IPM-DLCTCWs featuring single V-positioned magnets has been implemented and analyzed for traction applications. The system demonstrates a peak torque of 500 Nm, a peak power output of 200 kW, and a maximum speed of 10,000 r/min. The optimized motor is prototyped, and measurement results are provided.