Patent ID: 7576463

Claim:
A magnetic bearing device comprising: a rotor; a rotating member provided in the rotor; a radial magnetic bearing including a pair of radial electromagnets opposed to each other with the rotor interposed therebetween to support the rotor by a magnetic attraction force at a neutral position in a radial direction in a non-contact manner; an axial magnetic bearing including a pair of axial electromagnets opposed to each other with the rotating member interposed therebetween to support the rotor by a magnetic attraction force at the neutral position in an axial direction in a non-contact manner; a displacement detector which detects displacement of the rotor in the radial direction and the axial direction with respect to the neutral position and outputs the detected result as displacement information of the rotor; and a controller which supplies exciting currents, each including steady current and control current which varies in response to the displacement of the rotor, to the radial electromagnets and the axial electromagnets, respectively, to hold the rotor at the neutral position in the radial direction and the axial direction on the basis of the displacement information of the rotor obtained by the displacement detector, wherein the controller includes a calculator for obtaining first difference between values of the exciting currents supplied to the pair of radial electromagnets and obtaining a value obtained by multiplying the obtained first difference by a coefficient as a bearing load in the radial direction, and for obtaining second difference between values of the exciting currents supplied to the pair of axial electromagnets and obtaining a value obtained by multiplying the obtained second difference by a coefficient as a bearing load in the axial direction.