Eddy-current phenomena in ferromagnetic materials

THIS ARTICLE presents a new treatment of eddy-current phenomena in solid iron and other ferromagnetic alloys based upon a suggestion by A. G. Ganz.¹ The new treatment is developed logically, beginning with the familiar problem of eddy currents in an infinite region of constant permeability, bounded by a plane surface where excitation is applied. The concepts of phase shift and damping always associated with the space distribution of eddy currents found in this problem are extended to the case in which a ferromagnetic material is used. This material is assumed to have infinite permeability at zero field intensity between positive and negative saturation induction, with zero incremental permeability for all field intensities different from zero. A field theory consistent with the Maxwell theory and preserving the concepts of phase shift and damping is evolved for the assumed material.