Influence of Additional Air Gaps Between Stator Tooth and Back-Iron on Acoustic Performance of Spoke-Type Permanent Magnet Synchronous Motor

In this paper, the influence of additional air gaps between stator tooth and back-iron on the acoustic performance of spoke-type permanent magnet synchronous motor (STPMSM) is studied. It is found that the existence of these gaps can reduce the electromagnetic vibration noise, and its sound pressure level decreases by 2.3dB. By comparing radial electromagnetic forces acting on the stator, it is found that the additional air gap will weaken the 2-order radial electromagnetic force in space, which leads to the reduction of electromagnetic vibration noise. In order to further consider the influence of non-uniform additional air gap, the electromagnetic force is decomposed by two-dimensional fast Fourier transform (2D-FFT). The results of space-time spectrum show that the non-uniform air gap will introduce new space-time components of electromagnetic force, but it will not have a great impact on the acoustic performance of STPMSM. In addition, several commonly used stator tooth segments and back-iron segments are compared, which have different shapes of additional air gaps. The results show that the structure with triangular separated stator tooth and back-iron has better acoustic performance.