Design Consideration for Performance Improvement in One-Axis Actively Positioned Single-Drive Bearingless Motor

This paper presents rotor structures to enhance the active axial force in a single-drive bearingless motor. The single-drive bearingless motor can generate both torque and active axial force by q- and d-axis currents, respectively, with only one three-phase inverter. The axial z-axis position is actively regulated, but the other axes, radial and tilting movements, are passively stabilized. In this paper, the rotor structure is improved to enhance the active axial force. The active axial force and the other important performance parameters are calculated in three-dimensional finite-element-method analysis. In addition, the performance is comprehensively evaluated.