A Novel Single Winding Structure and Closed Loop Control of the Suspension Force Vector of Bearingless Permanent Magnet Synchronous Motors

At present, because of their advantages of simple structure, low cost, low power consumption and high efficiency, single winding bearingless permanent magnet synchronous motors (SBPMSMs) have become one of the research hotspots in the bearingless technology field. However, a high motional-electromotive force (EMF) is generated by rotor rotation in the single winding, which already has side-effects on the normal suspension force current, and the suspension force response can be delayed. Because the method of double torque current inverse injection in the symmetrical winding allows the motional-EMFs of the corresponding phase windings to offset each other in the opposite direction, with no adverse effects on original performance, a T-shaped single winding configuration is proposed to realize precisely that effect. In this paper, the analytical expressions of the radial suspension force and torque are deduced and the motional-EMF and performance are analyzed by finite element method using the Ansys-Maxwell software. In addition, a suspension force vector closed loop control strategy is proposed to improve the suspension performance. The complete control strategy of torque and suspension force is designed based on the above motor winding configuration. Finite element analysis (FEA) is used to verify the T-shaped winding structure. The control strategy is demonstrated by software (MATLAB) simulation and an experimental prototype. These results show that the winding structure and the control strategy can achieve the desired effect, improving the radial suspension force.