# Influence of Interference Fit and Temperature on High-Speed Permanent Magnet Motor
## 5 Conclusions  
In this paper, the main influencing factors of the interference fit structure of a high-speed permanent magnet motor are analyzed, and the problem of the thermal failure of the rotor system is systematically studied. The results and research significance are as follows:  
1. A design method to reduce the edge stress concentration of the interference fit structure is proposed. The problem of stress concentration is improved by adding chamfer to the end covers of the interference fit structure. Through adding chamfers to the end covers, the maximum stress of the structure is reduced from 1186.1 MPa to 308.42 MPa, which effectively reduces the stress of the structure. This could provide a basis for the design of the structure. 2. The reliability of the interference fit structure decreases as the amount of interference increases in the range of effective interference. When the rotational speed reaches 136,000 rpm, the structure will suffer loose speed and fail. In the actual working situation, when the speed of the high-speed permanent magnet motor approaches the critical speed, it is necessary to pay attention to the operation of the motor, and the speed cannot exceed the limit to avoid rotor structural failure and safety accidents. The wall thickness of the sheath should be appropriate to achieve sufficient preload while the interference fit structure meets the strength requirements and plays a role in protecting the magnet. To ensure the reliability of the rotor system strength, the operation of a high-speed permanent magnet motor can be stable. 3. The rise in temperature in the rotor system has a small effect on the stress of the sheath, but the stress on the magnet and end covers increases with the rise in temperature. According to the simulation results, it can be seen that when the temperature reaches 183.11 \({}^{\circ}\)C at 60 \(\upmu\)m, the strength of the structure fails. Considering the safety, the failure temperature of the interference fit structure at different interference values is analyzed. The results show that the operating temperature of the rotor system should not exceed 180 \({}^{\circ}\)C as far as possible in practice. In necessary cases, heat dissipation measures for high-speed permanent magnet motors, such as air-cooling of the rotor and water-cooling of the external shell to indirectly reduce the operating temperature of the rotor, so as to ensure the reliability and safety of the system during operation. It is necessary to acknowledge the limitations of this study. In the simulation, some minor influencing factors are normalized. In the actual working environment, the factors affecting the operation of a high-speed permanent magnet motor are not limited to the discussion in this paper. The findings in this study can provide a reference for designing the rotor structure of a high-speed permanent magnet motor, and a future study with a larger cohort size is needed to test the specific parameter requirements in practice. Conceptualization: Y.Z. ; methodology: Y.Z. and S.Y. ; software: Y.Z., Q.W. and J.H. ; validation: Y.Z., X.Y., Q.W. and W.H. ; formal analysis: S.Y. ; investigation: Y.Z. ; resources: Y.Z. and X.Y. ; data curation: Y.Z. ; writing--original draft preparation: Y.Z. ; writing--review and editing:  
Figure 18: The total deformation and strain distribution under different thicknesses of sheath wall. Y.Z. and S.Y. ; visualization: Y.Z. ; supervision: L.Z. ; All authors have read and agreed to the published version of the manuscript. This research was funded by Research and development of air bearing centrifugal compressor for hydrogen energy vehicles, grant number K4040121332. And the APC was funded by Northwest A&F University. Data Availability StatementData available on request due to restrictions eg privacy or ethical. The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy. The authors declare no conflict of interest.