Vibration Investigation of Spoke-Type PM Machine With Asymmetric Rotor Considering Modulation Effect of Stator Teeth

In this article, we analyze the vibration of the spoke-type permanent-magnet (PM) machine with an asymmetric rotor considering the modulation effect of the stator teeth. First, the semianalytical expression of the radial pressure is derived to quickly estimate the radial pressure characteristic. The equivalent spatial order of the radial pressure is determined by considering the modulation effect. Second, a structural finite-element (FE) model is set up. The modal test validates the accurateness of the structural FE model and modal analysis. Third, the vibration is predicted by an FE method and verified by the experimental results. The results show that the radial pressure harmonics become richer, and the fundamental frequency and lowest nonzero order of the radial pressure are both reduced due to the asymmetric magnetic barrier. Furthermore, the zero-order radial pressure is no longer the dominant vibration source in this integer-slot PM machine with an asymmetric rotor. Some high-order radial pressures that can be modulated as equivalent low-order harmonics excite the low-order and large vibration. In terms of vibration and noise, the equivalent lowest nonzero-order harmonic should be fully considered in the performance optimization for the asymmetric rotor design.