Axially and radially controllable magnetic bearing

Abstract

An axially controllable magnetic bearing apparatus provides radial stiffness force control between a rotor and stator. The bearing includes a pair of axially spaced air gaps defined by corresponding pairs of annular pole pieces of the rotor and stator. Permanent magnets carried by the rotor generate constant axial bias fluxes in each of the air gaps. A pair of coils, disposed to axially excite the air gaps with variable flux, are driven in a manner so that the sum of the total fluxes in each of the air gaps is varied to change the radial stiffness between the bearing rotor and stator. Axial force between the rotor and stator is produced by exciting the two coils to vary the difference of the total air gap fluxes. The pair of coils are driven in a bridge circuit by pulse-width modulated signals. The radial stiffness force of the bearing is varied in response to a control system for radially damping the bearing rotor and/or for shifting the vibrational resources of the bearing to avoid a vibrational resonance condition.

Dependencies are inferred from the claim text.