CONTROLLED MAGNETIC BEARING

PURPOSE:To make power amplifiers compact, heighten the stiffness of a magnetic bearing for a high-speed rotary machine and stabilize the control of the bearing, by composing the control circuit of the magnetic bearing of a rotary shaft rotational frequency detection circuit and whirl component elimination circuits which operate on the basis of the detection signal of the detection circuit. CONSTITUTION:The radial displacement of a rotary shaft 32 is detected by position detectors 40, 41, the output signals of which are compared with the position set signals of position setting circuits 45, 46 by comparator circuits 47, 48. The output signals of the comparator circuits 47, 48 are processed through compensation circuits 49, 50 and the band-pass filters 57, 58 and subtraction circuits 59, 60 of whirl component elimination circuits. Cutoff frequncy set signals produced by processing the output signal of the position detector 41 through a rotational frequency detection circuit 42 and converters 55, 56 are applied to the band-pass filters 57, 58 so that the filters send out only whirl components synchronized with the rotational frequency. The subtracters 59, 60 remove the whirl components. The outputs of the subtracters are applied to amplifiers 53, 54. According to this constitution, the amplifiers 53, 54 can be made compact.