SURFACE INTEGRALS ON 3D AND 2D FINITE-ELEMENT MODELS FOR SKIN EFFECT EXCITATIONS AND OPEN BOUNDARIES

Surface integrals on three dimensional finite element models can be used to excite currents in conductors with skin effects and to approximate open boundaries. In both cases the surface integrals are inhomogeneous Neumann boundary integrals which do not increase matrix bandwidth nor destroy its symmetry. To excite total conductor currents in skin effect problems, new inhomogeneous Neumann excitations are used. To represent open boundaries, the surface integrals are transformed into new Asymptotic Boundary Conditions. Example analyses include a 3D rail gun with transient skin effects, a 2D air core electromagnet with open boundaries, and three-phase AC bus bars having both closed and open boundaries. Results for the electromagnet agree with theory within 2 parts per million.