Design and test result of novel single-drive bearingless motor with cylindrical radial gap

In this paper, a novel single-drive bearingless motor with the cylindrical radial air-gap is proposed. The single-drive bearingless motor has only one set of three-phase windings. It generates both torque and axial suspension force independently with 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 direction z-axis is actively positioned. The other axes, radial movements x and y, and tilting movements θ_x and θ_y, are passively stable. In the proposed bearingless motor, the rotor is a cylindrical permanent magnet magnetized in a radial parallel direction. The stator consists of six C-shaped cores and one set of three-phase windings. The principles of the suspension force and the torque generations by the d- and q-axis currents, respectively, are shown. The test machine is fabricated and tested. In the experiments, the start-up is successfully achieved. In the acceleration test up to 3600 r/min, the stable magnetic suspension and the speed regulation by the d- and q-axis current regulation are confirmed.