## 6 Conclusions  
In this paper, an electromagnetic optimization design of a 60 kW, 30,000 rpm HSPMM is carried out. On the one hand, the mechanical strength of the rotor is taken into account in the optimization process. On the other hand, in order to obtain a more reasonable temperature distribution, the maximum motor efficiency and the minimum rotor core loss are selected as the optimization objectives.  
This paper introduces a multi-physics field optimization design approach for high-speed permanent magnet motors, streamlining the optimization challenges induced by the coupling of multiple physical fields. Firstly, according to the rotor stress and rotor dynamics finite element analysis results, the value range of the rotor key parameters is determined. Secondly, according to the subspace optimization strategy, the electromagnetic performance and loss multi-objective optimization problem is divided into rotor important parameter subspace and stator important parameter subspace, and multi-objective optimization design is carried out, respectively. On the one hand, the dimensionality reduction optimization of high-dimensional optimization space is realized, on the other hand, the accuracy of Kriging proxy model is guaranteed. Finally, according to the results of electromagnetic performance and loss multi-objective optimization, the temperature field of the designed HSPMM is checked.  
After multiphysics optimization design, the efficiency increased by 1.01% and output torque of the motor increased by 1%. the eddy current loss of PM reduces 64.7% and the thermal load of the motor reduces 6.1%. The results of three-dimensional finite element analysis of temperature field show that the overall temperature rise of the motor decreases obviously before and after optimization, and the maximum temperature decreases from 127 \({}^{\circ}\)C to 119 \({}^{\circ}\)C, decreased by 6.3%. The optimization effect is obvious.  
Finally, according to the final optimization results, an experimental prototype is designed and manufactured. The experimental results are basically consistent with the finite element analysis results, which further verify the accuracy of the finite element  
Figure 14: The comparison of the FEA results with the experimental results. (**a**) No-load line back EMF. (**b**) Load current.  
analysis results and the effectiveness and rationality of the proposed multi-physical field optimization design method for HSPMM.  
Conceptualization, H.Y. and G.D.; methodology, H.Y. and W.G.; software, W.G.; validation, H.Y., G.D., C.C. and K.X.; formal analysis, W.G. and Y.C.; investigation, H.Y. and W.G.; resources, H.Y.; data curation, H.Y., Y.C. and W.G.; writing--original draft preparation, W.G.; writing--review and editing, H.Y., G.D., W.G. and C.C.; visualization, Y.C. and W.G.; supervision, G.D.; project administration, H.Y.; funding acquisition, G.D. All authors have read and agreed to the published version of the manuscript.  
Key Research and Development Program of Shaanxi, 2024 GX-YBXM-243. Outstanding Youth Science Fund of Xi'an University of Science and Technology.  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors declare no conflict of interest.