Modeling of Bearingless Permanent Magnet Synchronous Motor Based on Mechanical to Electrical Coordinates Transformation

A bearingless permanent magnet synchronous motor(BPMSM) has two sets of stator windings, namely torque windings and suspension force windings, so there are two types of air-gap magnetic fields, torque windings’ and suspension force windings’, with different pole-pair in the motor. The analysis of the flux linkage intersection between the two sets of the windings is the foundation of setting up the precise mathematical model of the motor. By the application of mechanical-to-electrical coordinate transformation, this paper refers to a detailed analysis of the flux linkage intersection between torque windings and suspension force windings. And it has been proved that if the pole-pair of torque windings and suspension force windings are PM=1 and PB=2, respectively (or PB=1, PM=2), flux linkage of the torque windings and suspension force windings will be mutual coupling. The whole proof is simple, objective and easy to understand with a clear concept. What’s more, based on the conclusions proved above, the general mathematical model of BPMSM is set up. Finally, the experiment results have shown that the established mathematical model is feasible and accurate.