Drop dynamics of a high-speed unbalanced rotor in active magnetic bearing machinery

The transient nonlinear dynamics of a high-speed unbalanced rigid rotor dro pping onto rigid sliding bearings is investigated. The equations of motion are formulated and solved numerically to examine dynamics of the rotor for different regimes of the touchdown process. The contribution of parameters such as unbalance, air gap, coefficient of friction, and coefficient of res titution to drop dynamics of the rotor are examined. When the unbalance is small, the resulting motion is also small. As the level of unbalance increa ses, the motion of the rotor becomes larger, so there is potential for dama ge to the rotor and the backup bearings. The orbits of the rotor in the bac kup bearings after the rotor drops, velocities, and power loss during slidi ng-whirling stages are presented for various initial conditions and system parameters. Finally, based on simulation results, some design guidelines an d suggestions are given.