| 摘要 |
PURPOSE:To reduce generation of heat in excitation coils, by forming the excitation coil of an electromagnet only with a control coil further adding a bias signal to and subtracting it from a displacement signal so as to control the two electromagnets on the basis of these signals. CONSTITUTION:Two electromagnets 9a, 9b, provided in a symmetrical position with respect to a rotary shaft 2, form their excitation coils only by control coils 10, and a position sensor 3 detects a position of the rotary shaft 2 in its radial direction further in a direction parallel to a line connecting the electromagnets 9a, 9b. A detection signal from the position sensor 3 is converted into a displacement signal Vc phase compensated by a control circuit 4 having a phase compensating circuit or the like. Positive and negative bias signals DELTAVc are added to the displacement signal Vc by adder circuits 11a, 11b. Then the first rectifier circuit 12a allows the signal to pass if the addition Vc+DELTAVc is positive, while the second rectifier circuit 12b allows the signal to pass if the subtraction Vc-DELTAVc is negative. |
