The Coupling Effect of Manufacturing Tolerances and Rotor Eccentricity on Cogging Torque

Manufacturing tolerances and rotor eccentricity are two typical manufacturing uncertainties in actual permanent-magnet (PM) motors, which lead to the deterioration of cogging torque. In this paper, a vector analysis method is proposed to theoretically explain the coupling mechanism of manufacturing tolerances and rotor eccentricity on the additional harmonic components (AHCs) of cogging torque. First, the AHCs of cogging torque introduced by the respective impacts of manufacturing tolerances and rotor eccentricity are summarized. Then, the coupling effect of manufacturing tolerances and rotor eccentricity on the amplitudes of these AHCs is analyzed based on the proposed method, and its efficacy is verified through finite element simulations. It is found that the coupling effects in PM motors with varying parameters and uncertain values are distinct, and the reason is discussed. Subsequently, the proposed method is used in the modification of the worst-uncertain-combination-analysis method to evaluate the robustness of cogging torque under comprehensive manufacturing uncertainties. Finally, prototypes with different combinations of uncertainties are deliberately designed and tested, and the coupling effect is verified by the experimental results.