Perturbation expansion with separated time dependence for eddy current calculations

A particular solution to the eddy current integro-differential equations is found in the form of a perturbation expansion with separated time dependence. No reference to field values outside the conductor is required and a full three-dimensional treatment is maintained. Transient behavior of the eddy currents is obtained by this method through the technique of fitting the time variation of the driving field with a polynomial in time. As an example, the case of a thin plate of constant conductivity is studied. The eddy current distribution is obtained as a function of time for the external magnetic field of a dipole having ramp time dependence, and with the dipole axis perpendicular to the plate. The effects of the boundary charges in modifying the eddy current pattern are illustrated