Magnetic bearing apparatus and rotating machine having such an apparatus

A magnetic bearing control apparatus for controlling a magnetic bearing assembly including a magnetic bearing with a rotor and electromagnets for rotatably supporting the rotor by magnetic force, said control apparatus comprising:

• a magnetic bearing controller including displacement detecting means for detecting the displacement of the rotor from a predetermined position and providing a displacement signal indicative of the detected displacement;
• a compensating circuit for determining magnitudes of currents to be applied to the electromagnets of the magnetic bearing so as to hold the rotor at a predetermined position, on the basis of a displacement signal;
• and current amplifiers for controlling the currents of the electromagnets on the basis of an output signal of said compensating circuit;
• a simulating circuit for estimating the position of the rotor from the output signal of said compensating circuit;
• first subtracter for subtracting the output signal of said simulating circuit from the displacement signal;
• a feedback circuit, for compensation of a run-out, to which the output of said first subtracter is inputted;
• and
• a second subtracter for subtracting the output signal of said feedback circuit from the displacement signal,
• wherein the output signal of said second subtracter is set to an input signal of said compensating circuit and a signal to be subtracted of said first subtracter as a displacement signal, and
• said feedback circuit includes memory means for storing the output of said delay circuit, and supplying the stored signal to said delay circuit for at least two continuous periods.

In a rotating machine including a rotor, a magnetic bearing apparatus having a magnetic bearing for rotatably supporting said rotor by magnetic force, and a stator in which said magnetic bearing and said rotor are enclosed, the improvement wherein said magnetic bearing apparatus comprises:

• a magnetic bearing controller including displacement detecting means for detecting the displacement of said rotor from a predetermined position and providing a displacement signal indicative of the detected displacement;
• a compensating circuit for determining magnitudes of currents to be applied to the electromagnets of said magnetic bearing so as to hold said rotor at the predetermined position, on the basis of the displacement signal;
• and current amplifiers for controlling the currents of said electromagnets on the basis of the output signal of said compensating circuit;
• a simulating circuit for estimating the position of said rotor from the output signal of said compensating circuit;
• a first subtracter for subtracting the output signal of said simulating circuit from the displacement signal;
• and
• a second subtracter for subtracting the output signal of said first subtracter from the displacement signal,
• wherein the output signal of said first subtracter is inputted to said compensating circuit and is inputted to the second subtracter as a further displacement signal to be subtracted.