Analytical Calculation of Maximum Mechanical Stress on the Rotor of Interior Permanent-Magnet Synchronous Machines

Abstract

This article investigates analytical methods for calculating mechanical stress on the rotor of Interior Permanent-Magnet Synchronous Machines (IPMSMs). First, two existing analytical methods for calculating the stress on rotor iron bridges were investigated using a flat-type IPMSM model. The calculations of centroid radii required by these methods were simplified by taking advantage of the symmetry. Then, an accurate function of the stress concentration factor (SCF) was developed to calculate the maximum mechanical stress (MMS) on the iron bridge from its reference stress. The trends of SCF and MMS changing with geometrical parameters were obtained during the statistical analysis of SCF. Using the proposed analytical method, MMS on the bilateral iron bridges of both flat- and V-type IPMSMs can be calculated accurately. Finite element analysis (FEA) shows that the proposed method has improved accuracy and generality in calculations of the MMS. The reliability of the FEA model and the proposed analytical method were further investigated in a plastic deformation experiment. Based on the experimental results, the limits of the stress models, selection of the failure criteria, and safety factor were discussed for high-speed IPMSM design.