Magnetic Suspension Force in an Induction Bearingless Motor with a Squirrel Cage Rotor

Abstract

Theoretical equations of magnetic force in an induction bearingless motor have been reported. In the bearingless motor, both 4-pole and 2-pole windings are stored in stator slots for torque and suspension force generation. In the analysis, squirrel cage rotor currents are considered. These currents are induced by both torque and suspension winding currents. Inductance matrix is represented by four sets of three-phase windings, thus 12×12 matrix is constructed. A simplification and reasonable assumptions are introduced to obtain understandable expressions for suspension force and torque representation. The rotor flux linkages in an induction bearingless motor are derived, and then, simulation model of suspension force is constructed. It is shown that the response and the phase of suspension force are delayed in a case of cage rotors.