Study on the Optimal Rotor Retaining Sleeve Structure for the Reduction of Eddy-Current Loss in High-Speed SPMSM

In the case of designing high-speed surface-mounted permanent magnet synchronous motor (SPMSM), the rotor retaining sleeve is inserted into the rotor to prevent the permanent magnet´s damage. It is quite an efficient way to consider manufacturability, but the sleeve becomes the major source of ohm loss in high-speed operation. In this paper, the high-speed motor for a turbo blower at the rating of 100 kW, 20000 r/min was introduced. To improve its efficiency, the retaining sleeve´s optimal design was needed. For this, parametric analysis on the shape of the retaining sleeve was carried out in a different type of motor. Within a range that meets the mechanical safety, sleeve designs have been changed. The effect of changing design variables of the sleeve was studied. This paper presents the optimized sleeve´s advantages in electrical efficiency from the results of the electromagnetic finite element analysis software. Finally, it suggests the optimal sleeve design to reduce eddy-current loss, which is related to motor shape.