Reduction of Rotor Vibration in Passively Stabilized Direction in Single-Drive Bearingless Motor

In this paper, an improvement of the rotor vibration in one-axis actively positioned single-drive bearingless motor (SDBM) with repulsive passive magnetic bearings is presented. The SDBM has only one set of three-phase windings. It generates both torque and active axial force independently driven by only one three-phase inverter and one displacement sensor. Therefore, the single-drive bearingless motors have the advantages of low cost and small size. Only axial z-axis is actively positioned. The other axes, radial movements x and y, and tilting movements ? x and ? y, are passively stable. Therefore, in the one degree-of-freedom (1DOF) bearingless motor, vibrations in the radial and tilting directions are serious problem. In this paper, an improvement method of the radial vibration in the 1DOF SDBM is presented. The principle of the radial vibration generation is shown. In the experiment, it is found that a correction of the rotor rotational angular position is effective for the radial vibration reduction.