Vibration reduction of one-axis actively position regulated single-drive bearingless motor with repulsive passive magnetic bearings

In this paper, vibration reduction of a one-axis actively positioned single-drive bearingless motor with repulsive passive magnetic bearings is presented. The singledrive bearingless motor has only one set of three-phase windings. It generates both torque and axial suspension 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 radial and tilting directions are passively stable. Therefore, the passive axis vibrations are one of serious problems. It is shown that the radial vibration is originated from the axial vibration. Especially, the second-order harmonic vibration with respect to the rotational speed is one of the main factors. In theoretical calculations, relationship between the axial and radial vibrations is derived. Additionally, the vibration reduction methods are proposed. Finally, it is confirmed that the radial vibration is reduced by 59 % in the experiments.