Novel Acoustic Failure Prediction Method for Active Magnetic Bearing Systems

For magnetic bearing manufacturers, the installation situations in systems in the field are often unknown and not accessible. Hence, the final system vibration spectrum with respect to excitations by operating the system and therefore mechanical resonances are unknown as well. But to avoid failure, they need to be known before the speed is initially ramped-up in a magnetic bearing suspended system. Therefore, there is a need for an experimental method to predict and prevent already at rotor standstill risks due to plant mechanical resonances. This article shows theoretically and experimentally that conventional magnetic bearing rotor displacement measurement is insensitive on mechanical system resonances. As a solution, two new acoustic response methods are proposed, which can completely detect the system mechanical resonances that will occur during operation already in the standstill levitating state. Furthermore, it is shown with application case studies that these methods can be used for condition monitoring to detect deteriorating changes in the system before rotor speed ramp-up.