Modelling and performance analysis on a bearingless fixed-pole rotor induction motor

Abstract

Both torque winding magnetic field and suspension force winding magnetic field induce currents in the rotor in conventional bearingless induction motors (BIMs). Owing to the induced currents of suspension force winding, the air gap magnetic field is affected, which results in amplitude and phase error of torque and radial suspension forces. To overcome such drawbacks, a novel BIM with a fixed-pole rotor is proposed, which is called bearingless fixed-pole rotor induction (BFPRI) motor. First, the structure of the BFPRI motor is designed and introduced. Second, the mathematical models of radial suspension forces and torque are deduced. Third, the corresponding electromagnetic characteristics, including induced currents, radial suspension forces, and torque, are investigated and compared with the conventional BIM. Finally, the prototype motor equipped with a fixed-pole rotor is constructed and experimental research is carried out. According to the finite element analysis and experimental results, for the proposed BFPRI motor, only the torque winding magnetic field induces currents in the rotor, which makes the precision of torque and radial suspension forces higher and improves the accuracy of the BIM control system.