Dynamics and Vibration of a Single Axis Active Magnetic Bearing System for Small-sized Rotating Machinery

We have been studying a single axis active magnetic bearing for small-sized and high speed rotating machinery as a trial. The trial model has very simple structure and is very small in size and light in weight. The model is composed of two passive radial magnetic bearings utilizing repulsionforce ()f'permanent magnets and one active magnetic bearing in axial direction. Experimental results show that an unstable vibration occurs when the rotor was driven over 15,OOOrpm. In this paper, we discuss the cause and mechanism of this vibration. On the basis of computer analysis using the model with gyroscopic effect, it is clarified that coincidence of the node for conical mode and the damper cause the unstable vibration. Finally, we discuss countermeasures of this vibration.