Parallel-motion-type eddy current damper model of ring magnet and conducting disk

Abstract

In a parallel-motion-type eddy current damper comprising a magnet and conducting plate, the magnet is assumed stationary, and the conductor moves parallel to the xy-plane of a static coordinate system O-xyz. In a previous study, we proved that when an arbitrarily dimensioned rectangular magnet and conductor are symmetrically positioned along both the x- and y- axes at an instant, the condition that “the gradient of scalar potential is zero” (GSPZ condition) is established throughout the conductor in a stationary-conductor coordinate system. For an eddy current damper comprising a ring magnet and conducting disk, the equations of the magnetic vector potential and scalar potential are different from those for an eddy current damper comprising a rectangular magnet and conductor. In this study, we verified whether the GSPZ condition can be applied to an eddy current damper comprising a ring magnet and conducting disk. First, using the three-dimensional finite element method (3D-FEM), we analyzed the eddy current distribution in an eddy current damper comprising a single ring magnet and conducting disk, and we found that the GSPZ condition is valid for an arbitrary diameter of the conducting disk. Second, we verified that the GSPZ condition can be applied to an eddy current damper comprising a combination of ring magnets with oppositely aligned magnetic poles and two conducting disks with arbitrary diameters. Third, we calculated the magnetic damping forces of both eddy current dampers using Fleming’s left-hand rule under the GSPZ condition (GSPZ-A method), and the results were in good agreement with those obtained using the 3D-FEM.

Keywords

• eddy current damper
• magnetic damper
• three-dimensional finite element method (3d-fem)
• gradient of scalar potential
• magnetic vector potential