Modeling and digital control system for bearingless permanent magnet synchronous motor based on magnetic energy equation

A bearingless permanent magnet synchronous motor (BPMSM) is a kind of high performance bearingless motor, which has the advantages of both PMSM and magnetic bearings. By analysing the flux linkage intersection between the two sets of stator windings, a new concept of mechanical/electrical coordinate transformation is put forward. According to this method, flux linkage equations of the two sets of stator windings are derived. Then the magnetic energy equation can be gained. After analysing the mathematical formula of various sort radial forces in the BPMSM, a complete mathematics model of radial suspension forces for the BPMSM is obtained. The electromagnetic torque equation of the BPMSM is derived based on the analysis of the role of Lorentz force in the BPMSM. Finally, a control algorithm of the experimental system is given and some test results are discussed. This mathematics model provides a theoretical foundation for modeling of BPMSM, experiment waveform analysis and structure design.