Abstract：In the design of a high-speed permanent magnet machine, the calculation and verification of rotor stress are very important, especially the stress of a permanent magnet. The existing research mainly focuses on the influence of shrink-fitting magnitude on rotor stress, but ignores the influence of shrink-fitting modes. The shrink fitting between the sleeve and the permanent magnet greatly impacts the rotor stress. Limited by the electromagnetic power, the stress margin left to the permanent magnet or sleeve is limited to improve the material utilization. If the difference of rotor stress under various shrink fitting modes is not considered in the design, the safety of rotor strength will be greatly reduced when the operating point of the machine is near the limit value of the material stress, which may even lead to the failure of the design of high-speed permanent magnet machine. Therefore, the influence of shrink-fitting modes on the rotor stress of high-speed permanent magnet machines should be addressed, and more attention must be paid to it when calculating the rotor stress. This paper studies the influence of shrink-fitting modes on the rotor stress of a high-speed permanent magnet machine. Firstly, the stress field mathematical model of the unified geometric model of each rotor part is established in two-dimensional polar coordinates. The radial and circumferential stresses of the shaft, permanent magnet, and sleeve can be solved under different boundary conditions. It can be concluded that the rotor stress is the sum of the rotational component and the surface pressure component. The tensile stress caused by rotation can be offset by the pressure from the sleeve, and the degree of offset is determined by the pressure applied by the sleeve. Therefore, to calculate the rotor stress accurately, it is necessary to accurately calculate the stress caused by rotation and obtain the pressure applied by the sleeve. It is easy to calculate the stress caused by rotation, while the stress offset by the sleeve pressure is more complicated due to the shrink fitting, so it is necessary to study the influence of shrink-fitting modes on rotor stress. Then, based on the stress field mathematical model, the analytical calculation method of rotor stress under different shrink-fitting modes is further obtained, and the influence of different shrink-fitting modes on rotor stress is analyzed. Finally, taking a high-speed permanent magnet machine with rated power of 50 kW and rated speed of 40 000 r/min as an example, the rotor stress under different shrink-fitting modes is calculated by the finite element method. When the magnitude of shrink fitting relative to the sleeve thickness cannot be ignored, different shrink-fitting modes will significantly affect the rotor stress, especially the core component permanent magnet. Therefore, it is necessary to select a better mode by comparing shrink-fitting modes to reduce rotor stress and improve the safety and reliability of the machine. This paper provides theoretical guidance for the design of shrink-fitting modes of high-speed permanent magnet machine rotors.
杨江涛, 王镇宇, 冯垚径, 黄守道. 高速永磁电机转子过盈方式对转子应力的影响[J]. 电工技术学报, 2023, 38(16): 4263-4273.
Yang Jiangtao, Wang Zhenyu, Feng Yaojing, Huang Shoudao. Influence of Shrink Fitting Modes on Rotor Stress of High Speed Permanent Magnet Machine. Transactions of China Electrotechnical Society, 2023, 38(16): 4263-4273.
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