EARTHQUAKE-PROOF TYPE MAGNETIC BEARING DEVICE

PURPOSE:To make variable of bearing rigidity for securing yield strength for low frequency vibration component by providing a means increasing electric current for a winding at the time of rated operation. CONSTITUTION:A gate circuit 15 compares output voltage from a rotation speed detector 12 with set voltage about -5--10% of a value corresponding to rated revolution speed, and opens a gate when the same becomes in larger voltage than set voltage. Further, output of a function generator 13 shall be of wave form in angular characteristic making resonance frequency of a rotor a skirt and making lower frequency than the same a peak. Signal of a position detector 2 is operated on a position deviation operator 4 here, and the result is input into an adder 7 together with signal from the gate circuit 15 via a proportional-plus-integrator 5 and a differenciator 6, and electric current for a winding 3 is controlled with a servocontroller 8. A bearing can be made in a bearing having yield strength against low frequency vibration component by making bearing rigidity variable optionally accordingly.