A Boundary Integral Formulation on Unstructured Dual Grids for Eddy Current Analysis in Thin Shields

A three-dimensional boundary integral method (3D BIM) capable of analyzing the magnetic field at extremely low frequency (ELF) next to thin conducting shields is presented. This novel approach is formulated in terms of global variables (loop currents), avoiding field discontinuities across the shield. Using non-orthogonal dual grids the unknowns can be defined on nodes, thus greatly reducing computing requirements compared to traditional Galerkin's formulations. The procedure is validated using an axisymmetric problem. It is shown that analytical and numerical results are in good agreement even at few millimeters from the shield surface.