Dynamic characteristics of eddy current dampers and couplers

Eddy current dampers are promising devices for the passive, semi-active and regenerative control of vibrations. The aim of the present paper is to model the dynamic behavior of eddy current dampers and couplers and, by extension, of resistively shunted synchronous motors with permanent magnets. The modeling approach uses Faradayʹs law for the computation of the eddy current; the torque is then computed from the Lorentz force acting on the conductors. The electromechanical model is valid under rather general conditions and can be interfaced to the model of a mechanical structure to describe the coupled behavior. The relevant equations are solved for constant speed, and for a small amplitude torsional vibration of the rotor. The constant speed operation is characterized by the torque to speed curve which is typical of eddy current couplers and induction machines. The torsional vibration operation is characterized by the mechanical impedance and is typical of eddy current dampers. The torque to speed curve and the mechanical impedance are influenced by the same parameters. The relation between them constitutes a valuable design tool as it allows one to convert the steady-state characteristics into a dynamic model and vice versa.