Magnetic field around an iron torus

The authors present a semianalytical solution of the magnetic field excited by an infinitely long current filament passing through the hole of an iron torus. This is the first 3-D analytical solution for a bounded multiply connected iron region. The solution can be of use when testing 3-D magnetostatic software. The solution is expanded by toroidal functions which are calculated by efficient algorithms. Computed results in the x-Y plane are given for an excitation of 1 A and torus relative permeability of 1000