Comparative Thermal Analysis of Two Permanent Magnet Machines With Improved Heat Dissipation for In-Wheel Traction Application

In this article, the thermal analysis of two permanent magnet machines, permanent magnet vernier machine (PMVM) and synchronous machine (PMSM), is carried out for in-wheel drive application. An improved heat dissipation design is proposed and utilized for the in-wheel motors. Firstly, the in-wheel motors are designed and compared, afterwords, two prototypes of PMVM and PMSM are manufactured. Secondly, the losses of two motors are investigated, e.g., copper loss, core loss, and PM loss. The loss distribution feature of two motors has figured out. Thirdly, the single hub-bearing design for two in-wheel motors is illustrated. Besides, the heat transfer coefficient is further calculated, then the lumped model of single-bearing design is clarified, where the good heat dissipation effect of single hub bearing can be demonstrated theoretically. To further validate the feasibility of analysis above, the CFD models of two in-wheel motors are built. The temperature rises under various typical operation conditions for in-wheel drive are simulated and compared. It is noted that the PM temperature rise in PMVM is much severer than that in PMSM, which threaten the operation safety. Finally, the efficiency maps, temperature rise of windings and rotor parts are measured, respectively, which can agree well with the simulated results. This article aims to provide a comprehensive thermal analysis of PM machines with improved heat dissipation design for in-wheel traction application.