Impact of mechanical stress on characteristics of interior permanent magnet synchronous motors

In this paper, we investigate the impact of mechanical stress on characteristics of interior permanent magnet synchronous motors from both results of measurement and calculation. First, the basic experiments by using stator cores with/without shrink fitting of housing are carried out. The measured iron loss is compared with the calculated results obtained by combined stress and electromagnetic field finite element analysis. Next, the measured torque and iron loss of the motor under load conditions are compared with the analysis that considers the mechanical stress caused by both the stator shrink fitting and the rotor centrifugal force. The measured and calculated results are found to be in good agreement. From these results, it is clarified that the mechanical stress causes not only an increase in stator iron loss, but also an increase in rotor iron loss, and a decrease in reluctance torque of interior permanent magnet synchronous motors.