An Improved Dynamic Model for Bearingless Induction Motor Considering Rotor Eccentricity and Load Change

In the process of establishing a bearingless induction motor (BL-IM) traditional dynamic model, the magnetomotive force of rotor winding, the influence of suspension winding on torque, and the influence of torque winding on radial force are ignored. To solve the problem of insufficient accuracy in the traditional analytical model, based on fixed-pole rotor structure designed by the research group, which comprehensively considers the effect of suspension winding, torque winding, and rotor winding, an improved dynamic model is proposed. First, the spatial variation equation of air gap under rotor eccentricity is established, the composite magnetomotive force of three sets of windings according to the law of magnetic circuit is deduced, and the analytical model of magnetic coenergy in air gap is built. Second, using virtual displacement theorem to find partial derivative, the torque and radial force analytical model are obtained. Third, the improved BL-IM dynamic model is established. Finally, finite element analysis simulations based on controlled variable method prove the accuracy of improved dynamic model. The change trend of torque is verified with respect to suspension current, phase difference between suspension current and torque current, as well as rotor eccentricity. The change characteristics of radial force under no-load, load, and load disturbance are analyzed. In experiments, the controllers based on the traditional dynamic model and the improved dynamic model are compared and analyzed for speed, radial displacement, and centroid trajectory. The effectiveness of the improved dynamic accurate model is verified.