A systematic approach for modeling and identification of eddy current dampers in rotordynamic applications

Eddy current dampers (ECDs) exploit Lorentz forces due to the induced eddy currents in a conductor subject to a time–varying magnetic field. ECDs can be used to introduce damping in rotordynamic applications without mechanical contact to the rotor, thus introducing negligible impact on the dynamic response of the whole system. They are suitable for applications where contactless support of a rotor is required, thus being a perfect match for passive magnetic bearings such as permanent magnet bearings and superconducting bearings. However, modeling and identification of the amount of damping induced by ECDs is a difficult task due to complicated geometry and working conditions. A novel and systematic approach for modeling and identification of the damping characteristics of ECDs in rotordynamic applications is proposed in the present paper. The proposed approach employs an analytical dynamic model of the ECD and curve fitting with results of finite element (FE) models to obtain the parameters characterizing the ECD’s mechanical impedance. The damping coefficient can be obtained with great accuracy from a single FE simulation in quasi-static conditions. Finally, the accuracy of the identification approach is verified by comparing the results with experimental tests. The validity of this approach is in the cases where ECDs employ an axisymmetric conductor, thus covering most cases in rotordynamic applications.