Investigation of the Stress Concentration Factor for Estimating Maximum Mechanical Stress of Interior Permanent-Magnet Machines

摘要

This paper investigates the stress concentration factor (SCF) for the calculation of the maximum mechanical stress (MMS) on the rotor of interior permanent-magnet machines (IPMMs). The key factors that affect the stress concentration on the rotor iron-bridges are identified using finite element analysis (FEA). Based on the FEA results, an accurate SCF function is developed particularly for V-type and U-type notches on the IPMM rotors using the polynomial surface fitting techniques. Moreover, the equivalent ring method (ERM) is improved to calculate the normal reference stress of the bridge. Then, by combining the proposed SCF function with the improved ERM, a new analytical MMS model which is more general and accurate is obtained. In order to verify the proposed function, MMS calculations were carried out using the new ERM-SCF MMS model for different rotor configurations at various speeds, which the results are compared with the values obtained from FEA. The comparison shows that the proposed method has improved generality and accuracy as it always has a consistent trend with FEA for different rotor configurations, while the traditional ERM is only valid for some specific rotor geometries with strict constraints on choosing geometrical parameters.