Simplified Configuration of a Two-DOF Actively Controlled Bearingless Motor Using Two H-Bridges

This paper introduces a new structure and topology of a two-degrees-of-freedom (DOF) actively controlled bearingless motor using only two H-bridges (four half-bridges). The proposed two-DOF controlled bearingless motor has two-phase integrated motor windings. The neutral point of each phase winding is connected to the middle point of the inverter’s dc power voltage. This bearingless motor, thus, offers common dq-axis current vector control for permanent magnet motor drive as well as radial two-DOF active positioning control of the rotor. In this paper, the suspension force and toque of the 2-pole/8-slot model are theoretically derived from the stored magnetic energy. The magnetic energy is calculated from the inductance matrix where each inductance component is derived with the air-gap magnetic flux distribution. The theoretically calculated results show how the suspension force and torque are regulated with the control currents. To verify the theoretical calculation, two-dimensional FEM analysis is performed. The FEM calculation demonstrates that the proposed bearingless motor topology with 2-pole/8-slot structure using only two H-bridges generates constant suspension force and torque.