# A Study on the Electromagnetic-Temperature Coupled Analysis Method for In-Wheel Motors
## 5 Conclusions  
Based on the analysis of the coupling factors of the electromagnetic field and temperature field of a 15 kW IWM, the coupling characteristics of the electromagnetic-temperature field of the IWM were analyzed by different coupling methods. Through this study, the following useful conclusions are drawn:  
1. The electromagnetic field and temperature field are coupled and interact with each other in the IWM. The electromagnetic characteristic influences the temperature distribution of the motor through iron core loss, winding loss, and PM loss. By comparison, the winding loss is the greatest heat source of the IWM. Among the influencing factors of the temperature on the electromagnetic characteristics, the resistivity of the stator silicon steel material and the winding copper material is the primary factor. 2. Because the coupling factors of the two fields mainly consider the above strong coupling factors, electromagnetic-temperature coupling analysis was carried out with the unidirectional coupling analysis and bidirectional coupling analysis methods. According to the comparison of the results, there were some differences in the calculation results of the two fields. The temperature of the stator windings, stator cores, rotor cores, and PMs calculated by the bidirectional coupling method \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Maximum Temperature (\({}^{\circ}\)C)**} & \multirow{2}{*}{**Torque (Nm)**} \\  & **Stator Core** & **Rotor Core** & **Winding** & **PM** & **Torque (Nm)** \\ \hline Unidirectional coupling method & 111.2 & 85.5 & 117.8 & 85.4 & 144.36 \\ Bidirectional coupling method & 117.95 & 89.8 & 126.2 & 89.8 & 133.62 \\ Relative difference & 6.1\% & 5.0\% & 7.1\% & 5.1\% & 7.4\% \\ \hline \hline \end{tabular}
\end{table} 
Table 8: The highest temperature of each component. Figure 20: Comparison of torque and maximum temperature of the IWM. 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 reached 7.4%. 3. The 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. Meanwhile, it should be pointed out that the coupling analysis of the two fields mainly considers the two strong coupling factors. If all the coupling factors of the two fields were considered in the coupling analysis, the results from the two methods would have a greater difference. This is worth considering in the coupling analysis. The research work in this paper provides a theoretical basis and useful ideas for the multi-field coupling analysis of IWMs. Conceptualization, D.T. ; data curation, Y.W. ; formal analysis, D.T., Y.W., and K.Y. ; funding acquisition, D.T. and K.Y. ; investigation, D.T. and C.M. ; methodology, D.T., Y.W., Z.Q., and C.M. ; project administration, D.T. ; software, Y.W. and Z.Q. ; supervision, D.T. ; validation, D.T., Y.W., K.Y., Z.Q., and C.M. ; visualization, K.Y. ; writing--original draft, Y.W. and Z.Q. ; writing--review and editing, D.T. and K.Y. This research was funded by the National Natural Science Foundation of China (grant number 51775320 and 51605265), and sponsored by the Key Technology Research and Development Program of Shandong (grant number 2019 GGX104069). The authors declare no conflict of interest.