US 5,666,013 A · Magnetic bearing

Abstract

By using a hysteresis amplifier for driving an electromagnet, a highly accurate electromagnetic bearing may be produced without the need for independent position detectors to maintain the levitated position of a rotor constant. In one embodiment, the electromagnetic bearing includes multiple electromagnets for levitating a rotor in a predetermined position. Multiple hysteresis amplifiers each supply a switching signal for driving each of the electromagnets. The switching frequency of the switching signals changes in accordance with the inductance of the electromagnets, which varies in accordance with the relative position of the electromagnets. A phase comparator detects the phase difference between the switching waveforms of each hysteresis amplifier. A loop filter supplies a target current value converted from an output of the phase comparator to the hysteresis amplifiers. By controlling the input signals to the respective hysteresis amplifiers to maintain the frequency of the switching signal output of the respective hysteresis amplifiers constant, the position of the rotor is also maintained constant. Accordingly, a magnetic bearing may precisely control the levitated position of a rotor without the use of position detectors.

Claims11

Dependent claims

An electromagnetic bearing comprising:

a rotor;
an electromagnet for magnetically levitating the rotor at a predetermined position;
a hysteresis amplifier for supplying an exciting current to the electromagnet;
and control means for controlling the exciting current supplied by the hysteresis amplifier in accordance with a phase of an output of the hysteresis amplifier.

1 more element

An electromagnetic bearing comprising:

a rotor;
a plurality of electromagnets for magnetically levitating the rotor at a desired position;
a plurality of hysteresis amplifiers each for driving a respective electromagnet with an output signal having a switching frequency dependent upon an inductance of the respective electromagnet;
a phase comparator for comparing a phase of the respective output signals of the hysteresis amplifiers and producing a phase error output signal;
and a loop filter for supplying an input signal to the respective hysteresis amplifiers depending upon the phase error output signal such that the switching frequency of the respective output signals of the hysteresis amplifiers is maintained constant by controlling the input signal of the hysteresis amplifiers.

2 more elements

Dependencies are inferred from the claim text.

Magnetic bearing

Life of this patent

Magnetic bearing

Life of this patent

Abstract

Claims11