Article ID: 18-32AC_OA
The active magnetic bearing (AMB) has many advantages compared with the conventional bearing. It is the most widely used bearing in many machine applications; such as centrifugal compressor, air blower, and turbo molecular pump. AMB applications must be equipped with auxiliary bearings system to prevent the damage to the impellers and motor in case of system failure. The auxiliary bearing is referred to as the touchdown bearing in this study. When a failure is occurred, the active magnetic bearing cannot support the rotor stably. Touchdown bearings serve as a backup for the active magnetic bearings to support the rotor during a drop-down failure event. Therefore, a properly designed touchdown bearing system is necessary to protect the active magnetic bearing assembly and other critical machine components from direct contact with the rotor during AMB loss in power outage events. This system uses a ball bearing as a type of touchdown bearing. A finite element based 2-DOF (two-degree of freedom) flexible rotor model is used to indicate the rotor behavior. The rotor model also considers the contact force between the shaft-inner race and ball bearing force based on Un-lubricated Hertzian contact models. This study presents a dynamic rotor simulation during a drop event applied in a magnetic centrifugal compressor. This simulation is built using MATLAB with rotor speed effect and touchdown bearing design to predict the rotor behavior based on the rotor orbit and response.
