Shell impedance conditions for steady state and transient eddy current problems

Surface impedance techniques are discussed as a useful means of predicting fields in eddy-current problems, since they circumvent the need to model the conducting regions themselves. Their use has been limited to steady-state problems, where the characteristic field penetration depth is much less than the conductor thickness. The technique is extended to more general problems involving thin-wall conductors and transient problems. The focus is on shell structures. Transient fields are shown for the infinite cylinder and spherical shells placed in a step function field