Characteristics of a bearingless induction motor

A bearingless induction motor with additional windings in the stator slots is proposed. Additional two-pole windings were wound with the conventional four-pole windings to produce radial magnetic forces. These forces, which control the position of the rotor shaft, are produced when magnetic fluxes from the two-pole windings cause an imbalance in the revolving magnetic field of the four-pole windings. Inductance functions were measured to derive the machine inductance matrix expression, and from this matrix the radial force and current relationships were found. Control circuits were designed and fabricated for a test machine. This test machine was successfully driven by the control circuits. A bearingless induction motor was successfully operated at speeds up to 6000 r/min