Identification and Optimization of Active Magnetic Bearing Systems Using Measured Nyquist Diagrams

An effective measurement and identification technique of the stability of active magnetic bearing systems is introduced. Frequency response is reduced into an open-loop transfer function and displayed as the Nyquist diagram. This shows the stability of the syste~ both qualitatively and quantitatively. This technique is applied both for the axial direction, and for the radial direction with a strong gyroscopic effect. Measured Nyquist diagrams along the radial direction clearly show the divergence of eigenvalues caused by gyroscopic effect. A guide to optimize the system is indicated for the safe high speed rotation of the machine.