FEM Model of Oscillating Ferromagnetic Yoke in the Magnetic Field of a Permanent Magnet With and Without a Short-Circuited Coil

Numerical simulation of the oscillating ferromagnetic yoke in the magnetic field of a cylindrical permanent magnet without and with a short-circuited multi-turn coil was performed. Finite-element method (FEM) analysis based on the fundamental Maxwell equations and the Maxwell stress tensor approach was used. Due to induction of eddy currents in the volume of the conducting yoke, as well as in the other parts of the magnetic circuit, eddy current damping (ECD) occurs. There is some influence of the current circulating in the short-circuited coil. The shift of resonance frequency of studied systems to the lower values in comparison to the solely mechanical system was more significant for mechano-electromagnetic systems without the short-circuited coil than for the same system with the short-circuited coil. Also, the damping was higher without the short-circuited coil than with the coil. Good agreement with results obtained from experiments, as well as from the simplified analytic model, was observed. It follows that the addition of short-circuited coil deteriorates the vibration control properties of the system based solely on the ECD.