Analytical Calculation of the Mechanical Stress on IPMSM Bridges with Decomposition of the Centrifugal Force

This paper presents a new analytical method for calculating the maximum mechanical stress (MMS) on the rotor of interior permanent magnet synchronous machines (IPMSMs). Firstly, a universal model applicable to most common types of IPMSM rotors is built for the analysis of mechanical stresses on their central and bilateral bridges. Then, the direction and magnitude of the elastic force distributed on each bridge are calculated using the elastic deformation principle. From the estimated force magnitudes, the average stresses of all bridges are calculated. In the end, a modified equivalent ring method and the stress concentration factors of all bridges are proposed to calculate the MMS. After calibrating the models with coefficients obtained from a finite element model based design of experiments, satisfactory accuracies are achieved in MMS calculations for both the central and bilateral bridges. The results provide general guidance on mechanical stress reduction by structure optimization of high-speed IPMSMs.