Abstract: In an electromagnetic bearing control apparatus for suppressing vibratory rotational motion of a rotor, a selective extraction unit is provided in servo-circuits which control currents being supplied to electromagnetic coils in accordance with x and y-component signals of radial displacement of the rotor such that the rotor is held in a predetermined radial position, and x and y-component signals delivered out of the selective extraction unit are crossed and inputted to the servo-circuits so as to be added in opposite polarities to processed x and y-component signals of radial displacement.

Abstract: The present invention reduces the resonance amplitude of the rotational frequency-synchronous unbalance vibration of a rotor supported by an electromagnetic bearing.To this end, the invention disposes an X-direction control servo circuit and a Y-direction control servo circuit each of which detects the deviation of the rotor from a desired position in the radial direction thereof and controls the rotor so as to be held at the desired position on the basis of the detection signal, and a tracking filter which is synchronous with the rotational frequency. Outputs from the filter are crossed to supply the Y-direction control servo circuit with the X-directional output and to supply the X-direction control servo circuit with the Y-directional output signal.