Exterior Boundaries
The Exterior Boundaries node is the default boundary condition of the Magnetic Fields, Currents Only interface. It is usually used with the Stationary Source Sweep with Initialization study step. The Exterior Boundaries adds a constraint over the boundaries of the model to the value of an equivalent source based on a monopole and dipole expansion of the physical sources, expressed as
where r = x-xs, and xs is the point that an equivalent point source is placed. Qm and Dm are the source contributions from the magnetic monopole and dipole, respective. They are computed as integrals over current sources expressed as
The Exterior Boundaries feature is designed to efficiently compute the lumped inductance matrix with the Stationary Source Sweep with Initialization study step. For other studies such as the Stationary study, it is computationally heavier. In these cases, to improve the efficiency, switch the Exterior Field Equivalent Source to User defined or use the Magnetic Insulation boundary condition to override it. One can also use the Infinite Element feature to remove the constraint over adjacent Exterior Boundaries.