Emulating single point bearing faults with the use of an active magnetic bearing

Abstract

The propagation of evolving mechanical faults in rotating electric machinery and their corresponding signatures in the machines’ electrical signals is still not elucidated thoroughly. This deficiency implies serious obstructions in the development of using those signals as a complete and reliable condition monitoring technology. This study presents a new method to translate single point outer and inner race bearing faults into specific movements of the rotor with respect to the stator. The method contains the excitation of a simplified mass-spring-damper bearing model by analytical constructed fault-related force functions. Furthermore, a novel approach in order to emulate those obtained specific fault-related rotor movements with the use an experimental test setup is described, dimensioned, simulated and validated. Replacing the drive-end bearing of the induction machine under test by an active magnetic bearing creates the opportunity to continuously manipulate the rotor's position. The estimated single point bearing fault-related rotor movements serve as set-point for the magnetic bearing, resulting in the achievement of a single point bearing fault emulator with high relevance and reproducibility. This study includes experimental results of an emulated single point outer race bearing fault on an 11 kW induction machine.