A Study on the Electromagnetic–Temperature Coupled Analysis Method for In-Wheel Motors

As the core component of in-wheel motor-driven electric vehicles, the in-wheel motor (IWM) directly affects the driving/braking performance of each driving wheel and the driving performance of the vehicle. The IWM operation involves a coupling of multi-fields, including the electromagnetic, temperature, flow, and mechanical fields, which influence each other. It is necessary to study coupling analysis methods to obtain accurate and consistent results. In this paper, a 15 kW in-wheel motor is taken as the research object. Based on the finite element model of the IWM, the coupling factors between the electromagnetic and temperature field, and the influence trend of coupling factors on the two fields are investigated. On this basis, considering the strong coupling factors obtained from the above analysis, the unidirectional coupling and bidirectional coupling analysis methods are used to analyze the electromagnetic–temperature characteristics of the IWM, and the comparative results between the two methods are discussed. It was found that the results showed the temperature of the IWM calculated by the bidirectional coupling method was higher than that obtained by the unidirectional coupling analysis method. The maximum temperature of stator windings calculated by bidirectional coupling was 7.1% higher than that calculated by unidirectional coupling analysis, and the effect on the relative difference of torque could reach 7.4%. Bidirectional coupling can more accurately reflect the variation of variables in the fields and the prediction of motor performance in the process of motor operation. The progress made in the electromagnetic–temperature coupled analysis method can provide a theoretical basis and useful ideas for the multi-fields coupling analysis of IWMs.