Modeling of a Bearingless Induction Motor Based on Accurate Analytic Method and Design of a Magnetic-Balanced Control Module

To enhance the suspension performance of a bearingless induction motor (BIM), the Maxwell force equation is deduced based on an accurate analytic method, and a novel magnetic-balanced module is proposed in this paper. Firstly, according to the Gauss theory, the expression of Maxwell force at the air-gap is obtained and it is divided into two parts of suspension force and unbalanced pulling. Secondly, considering the impact of high-order components of rotor eccentricity, the precise expressions of the two types of Maxwell force are changed into the form of infinite series, and their general formulas are concluded by mathematical induction. Based on analyzing the Maxwell force′s infinite series with different poles, a magnetic-balanced control module is proposed in the control system. Finally, the control system of the new type of BIM is constructed, and an experimental platform is built to verify its feasibility and superiority. By simulation and experimental results, it has been validated that the proposed BIM with magnetic-balanced module can effectively reduce the high-order components of rotor eccentricity and has a better suspension performance compared with the initial machine.