Surface-Impedance Boundary Conditions in Nonlinear Time-Domain Finite-Element Calculations

The authors propose a novel nonlinear time-domain extension of the well-known frequency-domain
surface-impedance method in computational magnetodynamics. Herein the 1-D eddy-current problem in a massive conducting region (semi-infinite slab) is considered via a number of exponentially decreasing trigonometric basis functions that cover the relevant skin-depth (or frequency)
range of the application at hand. The resulting nonlinear equations are solved using the Newton-Raphson method. The proposed method is elaborated for the magnetic-vector-potential formulation and validated by means of a simple 2-D test case.