Influence of Rotor Skew in Induction Type Bearingless Motor

A prototype induction type bearingless motor has been developed with 4-axis active position regulation. In the developed motor, a problem of serious axial oscillation is observed during high acceleration and deceleration of shaft rotation. In the worst case, the shaft touched down and magnetic suspension was not possible. In this paper, the cause of the axial oscillation is presented. The axial shaft oscillation is shown to be caused by the skew of rotor conductors. One possible solution has been proposed and its effectiveness is verified in a prototype bearingless motor.