Performance Improvement of a One-DOF Actively Positioned Bearingless Motor

Conventional bearingless motors and magnetic bearings with one- to five-degrees-of-freedom (DOF) active positioning require a number of inverter modules, windings, position sensors, and electromagnets. To reduce the size and power consumption of this type of motor, the authors previously proposed a one-DOF actively positioned bearingless motor, referred to as a single-drive bearingless motor that has only one three-phase winding set and one three-phase inverter. Although the successful non-contact operation of this motor was demonstrated previously, a rotor of the test machine ran up to only 800 r/min because of serious resonance. The aim of this study was to improve the rotation performance of the single-drive bearingless motor. The cause of the rotor vibration was a discontinuous distribution of the magnetic flux density in the air-gap. One possible solution has been proposed in this paper. The test machine with an improved rotor was successfully driven up to 2000 r/min.