Abstract: Disclosed is a magnetic bearing system capable of simplifying a demodulation operation and reducing a processing load associated with a magnetic levitation control. A carrier signal having a frequency fc is apply to a sensor through a filter. The sensor operates to modulate the carrier signal, and a difference amplifier operates to calculate a difference between the amplitude-modulated signal FAM (t) and a sensor reference signal Fstd (t). An A/D converter operates to A/D convert a difference signal Fsub (t) output from the difference amplifier to a discretized sensor signal. In the A/D conversion, a sampling frequency fs is set to satisfy the following relation: fc: fc=n·fs or fc=fs/2 (n is a natural number). Thus, the discretized sensor signal includes no carrier wave, and therefore a demodulation operation which has been previously essential can be simplified.

Abstract: A magnetic bearing device includes an electromagnet for supporting a member without contact; an excitation amplifier for supplying an excitation current to the electromagnet; a carrier wave generation device for generating a carrier wave; and a sensor device for modulating the carrier wave to output a sensor signal according to a position of the member. An A/D conversion device converts the sensor signal to a digital value, and a demodulation calculation device demodulates through a digital calculation process according to the sensor signal converted to the digital value. A control device controls the excitation amplifier according to a calculation result of the demodulation calculation device.

Abstract: A magnetic bearing control device includes a rotation speed sensor for detecting a rotational speed of a rotating member supported on an axial magnetic bearing and a radial magnetic bearing without contact, and a displacement sensor for detecting an axial displacement of the rotating member. A control unit outputs a control signal of the axial magnetic bearing based on a signal from the displacement sensor. A filter unit reduces a signal with a specific frequency from the control signal output from the control unit, and passes a remaining signal, and a driving unit drives the axial magnetic bearing based on the signal output from the filter unit. The filter unit includes several notch filters with different ranges of the specific frequencies, and a selection device for selecting at least one of the notch filters according to the rotational speed.

Abstract: Disclosed is a magnetic bearing system for use in a vacuum pump including a rotor provided with a rotary blade. The magnetic bearing system comprises a rotary shaft rotationally holding the rotor, a motor for rotationally driving the rotary shaft, a magnetic levitation section for supporting the rotor relative to a stator through the rotary shaft in a non-contact manner, a rotation detection section for detecting a magnetic pole position of the motor, a rotor-temperature detection section for detecting a temperature of the rotor, a carrier-wave generation section for supplying a common carrier wave to each of a plurality of sensors provided in the magnetic levitation section, the rotation detection section and the rotor-temperature detection section, and an A/D conversion section for sampling a sensor signal output from each of the sensors, in synchronization with the carrier wave.

Abstract: A vacuum pump includes at least one magnetic body located on a circle about a rotor rotational axis and having a Curie temperature within a rotor temperature monitoring range; an inductance detecting portion facing the circle so as to establish a gap between the circle and the inductance detecting portion, for detecting a change of magnetic permeability of the magnetic body as an inductance change when the magnetic body rotates; and a carrier generation device generating a carrier signal for providing in the inductance detecting portion. An A/D conversion device samples a detection signal of the inductance detecting portion synchronously with a carrier generation by the carrier generation device, and converts the detection signal to a digital signal. A determination device determines whether or not a temperature of the rotor exceeds a predetermined temperature, based on the change of the magnetic permeability of the magnetic body.

Abstract: An electromagnet configured to contactlessly support a body includes an excitation amplifier configured to supply excitation current to the electromagnet, a carrier wave generation device, and a sensor configured to modulate the carrier wave and to output a sensor signal. An A/D conversion device is included for converting the sensor signal to a digital signal at a sampling frequency such that the frequency range of the sensor signal is either higher than 1/2 times the sampling frequency and lower than the sampling frequency, or higher than the sampling frequency and lower than 3/2 times the sampling frequency. In addition, a demodulation calculation device for demodulating the digitized sensor signal and a control device for controlling the excitation amplifier are provided.

Abstract: A magnetic bearing control device includes a rotation speed sensor for detecting a rotational speed of a rotating member supported on an axial magnetic bearing and a radial magnetic bearing without contact, and a displacement sensor for detecting an axial displacement of the rotating member. A control unit outputs a control signal of the axial magnetic bearing based on a signal from the displacement sensor. A filter unit reduces a signal with a specific frequency from the control signal output from the control unit, and passes a remaining signal, and a driving unit drives the axial magnetic bearing based on the signal output from the filter unit. The filter unit includes several notch filters with different ranges of the specific frequencies, and a selection device for selecting at least one of the notch filters according to the rotational speed.

Abstract: A magnetic bearing device includes an electromagnet for supporting a member without contact; an excitation amplifier for supplying an excitation current to the electromagnet; a carrier wave generation device for generating a carrier wave; and a sensor device for modulating the carrier wave to output a sensor signal according to a position of the member. An A/D conversion device converts the sensor signal to a digital value, and a demodulation calculation device demodulates through a digital calculation process according to the sensor signal converted to the digital value. A control device controls the excitation amplifier according to a calculation result of the demodulation calculation device.