Calculation and Analysis of Motor Thermal Stress With or Without Eccentricity for In-Wheel Electric Vehicle Applications

The requirement of high-power density and the problems of high temperature and uneven air gap caused by environmental constraints make the alternating effect of internal temperature and related constraints between components during the operation of the motor for in-wheel electric vehicle. These effects and constraints will lead to thermal stress and concomitant deformation, and seriously affect the safe operation of in-wheel motors (IWMs) and vehicles. Aiming at the above problems, this paper takes a 15 kW IWM as the research object. Based on the analysis of the mutual coupling relationship between the multi-physics field, such as the electromagnetic field, the temperature field, the flow field and the structural field, a thermal stress analysis model of the IWM is established and verified firstly. Then, quantitative calculation of the thermal stress/strain state of the IWM with or without eccentricity is carried out under different working conditions. The analytical results show that the thermal load generated internally leads to the generation of uneven thermal stress and accompanying thermal deformation, and the maximum thermal stress (MTS) and maximum thermal deformation (MTD) do not appear on the same component. Although eccentricity does not affect the position of the MTS and the MTD, it has an important effect on the maximum value of the stress and deformation, especially the eccentricity exceeds 30%. The results also demonstrate that the permanent magnet (PM) is most significantly affected by the eccentricity.