Dropdown Analysis of High-Speed Thin-Shaft Coupled Rotor System Integrated with Three Active Magnetic Bearings

Rotating machines supported by Active Magnetic Bearings (AMBs) are also equipped with touchdown bearings (TDBs) to support the rotor in cases of power failure or overload of AMBs system. In these dropdown events, the TDBs absorb the impact of the dynamic loads. The simulation and analysis of the orbit responses from such dropdown events can be utilized to prevent critical damage to the machinery. To that end, this study presents the dropdown simulation of a megawatt class induction machine driveline, levitated on three AMBs. The driveline has two AMBs for the motor and one AMB supporting the impeller of a compressor on an extension shaft. The shafts are connected via a thin shaft coupling. The system is first levitated with the designed LQR controller. To simulate a dropdown event, the destabilized system is allowed to fall under the influence of gravity load at the three TDBs. The time domain displacement amplitudes of the FE model are generated for different contact conditions based on the tangential velocity of the rotor. The vibrational amplitudes with different values of unbalance forces are analyzed to identify the most critical bearing and determine the operational limits of rotor system.