AMB rotor drop initial transient on ball and solid bearings

The increasing number of critical path machinery applications using active magnetic bearing (AMB) technology has focused awareness on the necessity for proper design of the auxiliary (backup) bearings. These emergency bearings are required to support the rotor in the event of control system failure or to provide for operation during momentary overload conditions with the AMB control system still active. Full-scale testing of production machinery has demonstrated both successful rotor drops as well as limited cases of auxiliary bearing failure. The reliability required for critical path machinery makes it essential to completely understand what parameters control the nature of the rotor drop transients. The current research project is intended to help understand the dynamic behavior of the rotor/bearing/support systems in the case of total loss of AMB support. This work presents test results for the initial rotor drop transient for several backup bearing configurations. The cases reported are: rigidly mounted antifriction bearing, rigidly mounted solid bushings (lubricated and unlubricated), and two soft mounted solid bushing configurations.