Vibration characteristics of a rotor system in contact with a backup bearing: Cases with various failure patterns of the active magnetic bearing

When electric power for an active magnetic bearing ( AMB) is shut down during operation, the backup bearing plays an important role in stopping the rotor system safely. Recently, a flexible high-speed rotor supported by an AMB, operating above the first and second critical speeds, has been investigated. In this context, the vibration characteristics of the flexible high-speed rotor when interacting with the backup bearing system become important. In this article, the mathematical models for the contact and friction forces which exist during contact between the rotor and the backup bearing are considered, the rotation of the inner ring of the backup bearing is modelled, and the vibration characteristics of the rotor system are studied. By comparing the results of numerical simulations and experiments, the validity of the mathematical model of the backup bearing is confirmed. Moreover, the vibration characteristics of the rotor systems when various types of failures occur in the AMB are clarified both theoretically and experimentally.