Analysis of thermal performance of an outer-rotor Surface-mounted permanent magnet (SPM) motor for electric vehicles

Abstract

In this work, the heat distributions and maximum temperature variations of the rotor and stator in a SPM (Surface-mounted permanent magnet) motor were analyzed under different ambient temperatures (T _amb ) and current densities (J). To achieve this, the conduction heat transfer between each of the motor components, the forced convection heat transfer inside the motor, and natural convection heat transfer between the inside of the motor and outside air were considered under steady state flow conditions. At the same time, copper loss and core loss, which are the representative motor losses, were also considered to simulate the heat generation inside the motor. To improve simulation accuracy and save time, only one-ninth part of the motor was investigated, using Finite element analysis (FEA). From these results, the operating limit temperature and current density conditions of the SPM motor were studied. It was revealed that the temperature inside the motor increased linearly as the current density increased due to the effects of stack length and core loss, and the cooling effect of the air gap was observed in most cases. At the same time, limit ranges for the stable operation of the SPM motor were suggested under various current densities (J) and ambient temperatures (T _amb ). These results can be used as a database for the development of EV motor systems.