Axial electrodynamic suspension in a Hybrid bearingless motor with active and passive axial stabilization

抄録

　This paper describes a bearingless motor with both passive and active axial stabilization. Passive stabilization through Null flux coils in the shape of Figure-8 has earlier been proposed in various papers. As the electrodynamic force in the symmetrical configuration increases with the rotational speed, levitation can be achieved only after a threshold speed. The active control of axial force was not possible with the symmetrical rotor configuration. This paper proposes a modification to the stator coil circuit by connecting an external inductance to any one of the coils to achieve active control of axial force with an external supply. The axial force sufficient enough to compensate for rotor weight and any unstable axial forces can be achieved at low rotational speeds. Theoretical equations for axial forces have been derived and the results have been compared with FEA. The rotational speeds at which the levitation occurs have been estimated theoretically and experimentally.