Optimal Design on Bearingless Permanent Magnet Synchronous Motor to Decrease Losses and Torque Ripple

It is important to clarify the eddy current losses in permanent magnet rotor for temperature rising to induce irreversible demagnetization when the bearingless permanent magnet synchronous motor (BPMSM) is operating at high speed. In this paper, the torque and radial suspension force producing mechanisms of BPMSM are introduced. The relative motion relationships among radial suspension force, rotor magnetic field and suspension winding magnetic field are analyzed. The rotor eddy current losses in BPMSM with PB=PM+1 and PB=PM-1 are compared. At the same time, the radial suspension forces of different pole pair number surfacemounted permanent magnet rotors with the same stator are calculated and compared to reduce the suspension force ripples using 2D time-steeping finite element method considering the rotor rotation. The research results have shown that the BPMSM with PB=PM+1 is the most suitable for high speed operation with the minimum eddy current losses in rotor, bigger radial suspension force and smaller suspension force ripples. Copyright © 2014 IFSA Publishing, S. L.