Mitigation of Radial Force for Permanent Magnet Machines With Shifted Notch on Stator Teeth

This paper investigates the effect of the notches in stator teeth on the radial force and vibration of fractional slot concentrated winding permanent magnet machines. The radial force density (RFD) is analytically established considering the position of the notches in the stator teeth. It is found that the RFD can be reduced by optimizing the position of the notch, and the optimal notch shift angle to minimize the dominant RFD is also given. The reason for the reduction of the dominant RFD could be explained as the phase of the RFD components affected by permeance varies with the shifted angle of notch, resulting in a decrease in the amplitude of radial force when it is opposite to that of other components. For the machines having stator without notch, notch in the center of the teeth and shifted notch, the RFDs and vibration response are both calculated and compared by finite-element analysis. It is demonstrated that the machine with the shifted notch has the minimum dominant RFD amplitude and the lowest vibration level. Finally, prototypes with/without notching are manufactured and their modal frequency and vibration are tested for validation.