Patent ID: 6023115
Filing Date: 2000-02-08
Classification: F16C

Abstract:
In a three axis control magnetic bearing apparatus disposed in a frame of a motor, having a lower side permanent magnet disposed in one end of the frame, an upper side permanent magnet disposed in the frame so as to be facing the lower side permanent magnet and separated therefrom by a small gap, a metal disc disposed in the frame and having the upper side permanent magnet fixed to one side thereof and having a shaft of the motor passing through a central opening formed therein, an axial electromagnet for attracting the metal disc and supporting the shaft in mid air, and an auxiliary bearing for preventing mechanical damage from occurring in the event of breakdown of the axial electromagnet, the improvement comprising: a radial position correcting electromagnet disposed in the frame and having a magnetic pole extending in the direction of a radius of the metal disc, the radial position correcting electromagnet being disposed adjacent to the metal disc and spaced therefrom by a small gap and being responsive to a voltage having a short period applied thereto on the starting up of the three axis control magnetic bearing apparatus in the vicinity of a resonance point of rigid mode of the shaft, as the speed of the three axis control magnetic bearing apparatus reaches at least one predetermined speed, for attracting the metal disc to correct a radial position of the shaft to prevent excessive contact between the shaft and the auxiliary bearing in the vicinity of the resonance point of rigid mode.