Aseismatic Vibration Control on Active Magnetic Bearing Equipped Flexible Rotors.

The conventional type of large turbo machinery employing oil-film bearings is supported so stiffiy that the rotor is strong against earthquakes. However, there is concern about its reliability against rotors supported by Active Magnetic Bearings (AMB) because of its weak support. In this paper, a flexible rotor supported by AMB is selected for aseismatic evaluation. The shaking test using the actual earthquake Kobe and El Centro waves was done and the response vibrations were measured. The corresponding simulation was also done. According to experimental and calculation results, maximum response vibration is still less than the gap of touchdown bearing, i. e., norubbing vibrations and the safety requirement is thus satisfied. However, the response severity of AMB rotors is comparatively high with oil film bearing rotors. In order to reduce this sensitivity against earthquakes, we propose an additional control method using the feed forward excitation which force is proportional to the signal detected by the accelerometers attached on bearing housings. Since this addition 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 is proved for earthquake induced vibrations reduction.