Patent ID: 7977839

Claim:
A magnetic bearing device for rotatably supporting a magnetic piece in a levitating state at a specified position comprising: an electromagnet for supporting the magnetic piece in a levitating state by magnetic force; a displacement detection means for detecting a displacement of the magnetic piece based on impedance change in the electromagnet; and a driver for applying an excitation current to the electromagnet so as to support the magnetic piece in a levitating state at a specified position based on a detection signal from the displacement detection means; wherein the driver is a pulse width modulation type driver to control an excitation current of the electromagnet by modulating a pulse width of a pulse voltage driven at a specified carrier frequency, and the displacement detection means has a ripple detection means for detecting an amplitude of a ripple current generated by the driver applying a voltage to the electromagnet, and a signal contained in a signal detected by the displacement detection means other than the displacement information of the magnetic piece is removed by subtracting a signal obtained from an output signal of the displacement detection means passing through a filter means of characteristics equivalent to the transfer characteristics from getting current flow to the driver to current flowing in the electromagnets and through an amplifying means for amplifying with a specified gain, from a signal obtained from the ripple detection means.