Dynamics of a Rotor - Magnetic Bearing System Equipped with a Thrust Magnetic Bearing

This paper is concerned with the dynamics of a rigid rotor supported by journal and thrust active magnetic bearings. For small perturbation, the action of the thrust bearing can be described by a series of stiffness coefficients. The system equations are formulated by combining the equations of motion of the rotor and the equations of the decentralized PID controllers. The eigenvalues of system are calculated and examined. The results indicate that the thrust magnetic bearing has great influence on the eigenvalues corresponding to lowfrequency conical whirls, and causes the system stability to degrade.