Rotor Strength Analysis and Retaining Sleeve Design for High-speed Permanent Magnet Machines

Based on a two-dimensional (2D) analytical stress model, a design method for minimizing the rotor retaining sleeve thickness of high-speed permanent magnet machines (HSPMM) was proposed in this paper. The analytical model for calculating the 2D rotor stress field was established, which could take the combined influence of prestress, centrifugal force and thermal stress on an orthotropic material into account. The model was verified with finite element analysis, since experimental validation was not applicable for a high-speed rotor. The stress limit conditions of rotors with three types of common sleeve materials were determined through the analysis. The method of calculating the minimum rotor sleeve thickness and its corresponding amount of interference fit was proposed, which could suit the conditions of single extreme operation point and multiple extreme operation points, respectively. Applicable sleeve types were thus stated. For some conditions under which the magnets had insufficient tensile strength at hot state, the boundary equations were replaced to constrain the magnet stress, so as to obtain a safe sleeve scheme. The proposed method is sufficiently rapid, accurate and flexible, and can be applied to the multi-physics design of HSPMM. © 2022 Chin. Soc. for Elec. Eng.