Based on the linear field theory and the limiting nonlinear theory, respectively, the eddy current losses in thick iron plates and thin laminations are formulated. Two equivalent permeability calculation models are developed to take into account the saturation effects occurring in the corresponding ferromagnetic materials. By enabling the approximate treatment of the magnetic field saturation, the nonlinear eddy current problem is reduced to the linear one. The proposed approach to the linearization of the field analysis is investigated by comparing the results of the linear analysis using the equivalent permeability with those of the nonlinear finite element analysis and experimental data.@en