Field-circuit coupling for time-harmonic models discretized by the finite integration technique

This paper develops the coupling between a three-dimensional modified magnetic vector potential formulation discretized by the finite integration technique and a circuit including solid and stranded conductors. The conductor models relate local quantities defined at primary edges or dual facets and the global circuit unknowns. Two possible coupling matrices are derived which either affect the edges perpendicular to a reference cross section or all edges inside the conductor. To preserve the sparsity and the structure of the discrete field system, the circuit analysis is based on a circuit tree, incorporates both voltage drops and currents as additional unknowns, and results in a symmetric coupling. The numerical efficiency of both coupling approaches is compared for technical applications.