Dynamics of Active Magnetic Bearings

Abstract

A simple new model is developed to analyze the dynamics of active magnetic bearings. In the model, the time lag of the flux due to eddy current is considered, but the gyroscopic effect is neglected. Magnetic force is described by the flux instead of the coil current. This description converts the equations of rotor dynamics into a simple form, although the time lag of the flux should be assumed when the dynamics of the flux are unknown. In the frequency and impulse responses, the numerical analysis is compared with the experimental results of a radial bearing whose control system is constructed by a PID compensator with a single loop. The results show that the numerical analysis fits the experimental results well by assuming an appropriate time lag for the flux.