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To enhance the working efficiency of a bearingless induction motor with the specific pole (BIM-SP), an accurate modeling method considering the iron loss is proposed, and the optimal rotor flux-oriented control (ORFOC) strategy is studied in this paper. Firstly, the mutual inductance expressions with rotor eccentricity of the torque winding and suspension winding are deduced and verified theoretically. In addition, the two windings are converted into the same circuit and the composed mutual inductance is discussed. Secondly, the accurate equivalent circuit model on the d-, q-axis considering the iron loss is established, and the optimal rotor flux is figured out. Thirdly, by theoretical deduction, the rotor flux expression is directly turned into the function of the equivalent composed winding current, and the parameter identification method based on the simplified flux-current model is proposed to enhance the control accuracy. Further, the delayed field weakening (DFW) strategy is introduced in the control system to suppress the rotor vibration. Finally, an experimental platform is built to validate the practicality. Theoretical analysis and experimental results indicate that the adopted optimal rotor flux control both improves the motor efficiency and achieves an excellent levitation performance.
Ding et al. (Wed,) studied this question.