Abstract: Dynamical equations of a multi-disk multi-mass flexible rotor supported on active magnetic bearings drop on flexible rolling element backup bearings during power failure are developed by the finial element method, the transient nonlinear dynamics of the rotor drop on the backup bearings are analyzed on a multi-disk multi-mass flexible rotor and the influence of support stiffness, support damping and radial clearance of the flexible backup bearings on the transient behavior of the rotor is examined. It is shown the rolling element backup bearing with flexibility and more damping can greatly improve the dynamic behavior of a rotor drop on rolling element backup bearings, suppress the full clearance whirl motion with a large rotor vibration and impact force acted on the backup bearings, and decrease the effect of rotor drop on the life-time and reliability of backup bearings. The higher the support damping, or the smaller the support stiffness, or the larger the backup bearing’s clearance, the less the possibility for occurring the full clearance whirl motion is.

Key words: Active magnetic bearing, Backup bearing, Drop, FEM, Rotor