Internal impedancee of solid ferromagnetic conductors

Experimental data are presented, concerning the behaviour of ferromagnetic conductors carrying alternating currents, for a wide range of frequencies and values of the surface-magnetising force. The experimental results are for mild-steel conductors having rectangular and circular cross-sections. The object of the investigation was to study the influence of both saturation and type of cross-section on the impedance of the conductor. A linear two-dimensional theory is outlined, for the rectangular-section conductor, on the assumption that the current density at the surface is constant. It is further shown that the two-dimensional problem can be reduced to one of single dimension. The linear analyses explain qualitatively the experimental results. The conclusion drawn is that, for materials of high permeability, the conductor surface is a flux line, for all types of cross-section.