Basic Calculation of Axial Force and Torque with Permeance Method in One-Axis Actively Positioned Single-Drive Bearingless Motor

This paper presents mathematical calculations of active axial force and torque in a single-drive bearingless motor. The single-drive bearingless motor has only one set of three-phase winding. The active axial force and torque are generated by d- and q-axis currents, respectively. Only the rotor axial z-axis position is actively regulated. The other axes, radial movements x and y, and tilting movements theta-x and theta-y are passively stabilized. In this paper, the mathematical equations of the active axial force and torque based on a permeance method are derived. It is confirmed that calculated force and torque are corresponding with those of three-dimensional finite-element- method analysis.