Asymptotic boundary condition for three dimensional magnetostatic finite elements

An asymptotic boundary condition (ABC) is derived for open boundaries of three-dimensional magnetic vector potential magnetostatic finite element models. The boundary condition avoids any increase in matrix bandwidth and hence is computationally very efficient. The ABC is used on boundaries of three-dimensional finite element models of both a circular coil and a square coil; the computed magnetic fields or inductances of the two models agree within a few percent with Biot-Savart or classical solutions