Beaingless motors have the integrated functions of conventional magnetic bearings and motors. In this study, the linearized model of an induction type bearingless motor is proposed with the relations between air-gap flux density distributions and radial electromagnetic forces. The proposed bearingless motor has additional 2-pole control windings together with 4-pole motor windings in stator slots. The radial force for position control, which is linearly proportional to the magnitude of control currents, is synchronized to the rotating magnetic field generated by motor currents. The negative position stiffness is also analytically calculated, neglecting the coupled nonlinear effects. The laboratory bearingless motor is successfully levitated and rotated under no-load conditions.
