Analysis of Zeroth-Mode Slot Frequency Vibration of Integer Slot Permanent-Magnet Synchronous Motors

For the integer slot permanent-magnet (PM) driving synchronous motor, the zeroth-mode slot frequency vibration and noise play a significant vibroacoustic role in the low-frequency domain. For conventional analysis in literature, it is usually assumed that the zeroth-mode vibration is caused by the zeroth-order radial force harmonic. But in this paper, the genuine reason for zeroth-mode vibration is proposed and discussed in detail, which is different from the conventional analysis. The teeth chopping effect is proposed and demonstrates that the slot number order radial force is the root of the zeroth-mode vibration of the motor. After the analysis of the zeroth-mode vibration in existing research work is presented, the teeth chopping effect is introduced and described. The amplitudes of the zeroth-order and slot number order forces are compared with an analytical method, while their amplitudes and caused deformations of these forces are calculated with the finite-element method (FEM). Finally, to validate the analytical and FEM results, a 6-pole 36-slot PM driving motor is manufactured and tested, and the results are in good agreement with those of the FEM results.