An Aseismatic Control and Evaluation for Active Magnetic Bearing Equipped Rotors

Up to now, any rotating machine equipped with active magnetic bearing (AMB) is not employed in nuclear plants because of its low suspension stiffness. The wide application of AMB requires an aseismatic evaluation with respect to AMB rotor vibrations caused by actual earthquakes. In this paper, a flexible rotor supported by AMB is selected for this purpose. The shaking test using actual earthquake Kobe and El Centre waves was completed and measured for the vibration evaluation. The corresponding simulation by models obtained from the quasimodal method is also completed. According to these experimental and theoretical results, response vibrations of AMB rotors are very severe compared with conventional oil lubricated bearing. In order to reduce the response severity against earthquakes, we propose an additional feed forward control method, which is proportional to the signal detected by the accelerometers attached to the bearing housings. Since this additional control can act as the cancellation of rotor vibration generated by the earthquakes, AMB rotor vibrations are successfully suppressed at a low level. The effectiveness of this AMB control method for earthquake induced vibrations is demonstrated.