Zeroth-Mode Vibration Suppression Through Adjustment on Phases Difference of Concentrated Force Harmonics for PMSMs

Zeroth-mode vibration is the dominant noise source in permanent magnet synchronous machines (PMSMs). In conventional approaches, the zeroth-mode vibration is reduced by lowering the amplitudes of concentrated forces. Different from conventional approaches, this article proposes a zeroth-mode vibration suppression method through adjustment on phase difference of concentrated forces. First, the characteristics of concentrated forces are analyzed considering the effect of slotted structure on air-gap electromagnetic force wave (EMFW), and the relationship between phase difference of concentrated force harmonics (CFHs) and the mode of vibration is obtained. Subsequently, the effects of both permanent magnet (PM) and harmonic currents on air-gap EMFW are analyzed. It is found that the phase differences of CFHs can be adjusted by combining PM shape optimization and harmonic current injection. Finally, a 12-pole 36-slot PMSM and a 16-pole 48-slot PMSM are carried out to calculate the concentrated forces and vibrations by finite element method (FEM). It is proven that the proposed method can adjust the phase difference from zero to two tooth pitches, and the zeroth-mode vibration is significantly suppressed.