Impedance of Magnetic Coaxial Pipe

Abstract

It was found that a coaxial pipe consisting of two ferromagnetic pipes exhibits interesting properties, as the skin effect is considerable even at low frequencies when current is passed in the pipes. Among other results, it was found that the impedances of the inner and outer pipes Z <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in</inf> and Z <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</inf> were considerably different, and that there exists a current frequency at which Z <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</inf> is minimum. A qualitative vector diagram and quantitative formulae are presented relating the impedances to the current densities and magnetic fluxes in the pipes.