Optimization Design of Bearingless Permanent-Magnet Slice Motor

The parameter and distribution of air-gap flux density determined by structures and methods of permanent-magnet rotor magnetization have effects on the performance of suspension forces and torque in a bearingless permanent-magnet slice motor (BPMSM) directly. In this paper, different rotor structures and magnetization methods are analyzed for the BPMSM. Based on the finite-element analysis, the optimum length ratio of rotor magnetic yoke dr and lr is calculated in different magnetizations to get the maximum flux density. Then the radial suspension forces with maximum air-gap flux density in different structures and rotor magnetizations are compared for the BPMSM. The simulation and experiment results show that the amplitude and sinusoidal characteristic of air-gap flux density are improved with parallel magnetized ring-shaped rotor. Furthermore, the BPMSM with parallel magnetized ring-shaped rotor is easily controlled and has a good suspension and speed regulation performance.