A Vibration Reduction Method of One-Axis Actively Position Regulated Single-Drive Bearingless Motor With Repulsive Passive Magnetic Bearings

We present a method for reducing vibration in a one-axis actively positioned single-drive bearingless motor with repulsive passive magnetic bearings. The single-drive bearingless motor has only one set of three-phase windings. It generates both torque and axial suspension force, regulating the
$q$
- and
$d$
-axis currents, respectively, driven by only one three-phase inverter. Single-drive bearingless motors have the advantage of low cost. Only the axial
$z$
-axis is actively positioned. The radial and tilting directions are passively stabilized. Therefore, passive axis vibrations are one of the few serious problems. In this paper, we show that radial vibration originates in axial vibration. In particular, the second-order harmonic vibration with respect to rotational speed is a factor. In theoretical calculations, we derive the relationship between axial and radial vibrations. Additionally, vibration reduction methods are proposed. Finally, experiments confirm that radial vibration is reduced by 59%.