Patent ID: 9624974
Date: 2017-04-18
CPC Classifications: F04D,F16C,H02K,H02P

Claim:
1. A magnetic bearing device comprising: a pair of electromagnets provided for each of a plurality of control axes so as to face a rotor shaft; a plurality of excitation amplifiers configured to perform PWM control to a voltage applied to each of the electromagnets, and supply an electromagnetic current on which a sensor carrier signal for detecting a change of a levitation position of the rotor shaft is overlapped to each of the electromagnets; a plurality of current sensors each configured to detect the electromagnetic current; and a controller configured to obtain magnetic levitation information of the rotor shaft by AD sampling of current detection signals from the plurality of current sensors, and perform PWM control of the excitation amplifiers based on the magnetic levitation information, wherein a minimum period is set for an on-duty period or an off-duty period of a PWM control signal in a single PWM carrier cycle, the minimum period being longer than a predetermined time period based on an attenuation characteristic of a spike noise produced in the electromagnetic current, the controller performs PWM control so that a length of one of the on-duty period and the off-duty period is equal to or greater than the minimum period, and performs the AD sampling after the predetermined time period passes from starting timing of one of the on-duty period and the off-duty period.