Eddy-Current Losses in Slitted Rotor Cores of PMSMs—Development of a Novel Method

In recent years, high-speed PMSMs have gained popularity due to advancements in materials, manufacturing, and high-switching-frequency power electronics. However, the design and manufacturing of high-speed PMSMs presents challenges such as high centrifugal forces and complexities of thermal management. Solid rotor cores are used to address these issues, although they may suffer from high eddy-current losses. Slits on the rotor surface can mitigate these challenges. In the region without slits, the end effect is negligible, but in the slitted region, a significant end effect caused by current circulation in narrow areas must be considered. Traditional methods for calculating eddy-current losses are insufficient for such designs. In this study, firstly, the slit geometry is introduced, and it is explained why traditional FEM methods are insufficient to calculate eddy-current losses for such rotors. After that, a fast and reliable method for evaluating eddy-current losses in a slitted solid rotor is proposed. Experimental tests are carried out separately on scaled prototypes of the rotor with and without slits, and the results are compared with 2D and 3D FEM results. After the validation of the proposed method, it is used in the solid rotor of a PMSM. Rotor losses are compared in the PMSM equipped with different solid rotors, either with or without slits.