Transient Shielding of Conducting Screens

Abstract

In the literature the magnetic shielding effect of a screen has been u s u a l ­ ly treated in a simplified manner. In this paper, however, we show that the problem is more complicated. The object of investiga­ tion consists of a perturbing and a pertur­ bed line, both separated by a conducting screen, where the perturbing line carries an impressed current while the perturbed line is used to connect a load with a source of impressed voltage. The eddy currents in­ duced by the two lines in the screen as well as in the perturbed line depend on the load and on the geometry of the shielding system. For the description of the transient shield­ ing problem we use an integral equation, where the domain of integration extends over the cross-sections of the screen and of the perturbed line. The investigation of the system's shielding properties requires a solution to the eigenvalue problem of the integral equation which leads to a non-line­ ar matrix eigenvalue problem. In the case of alternating currents we replace the shielding system by an equivalent network model having frequency-dependent components. The paper contains the derivation of the general theory. Its results can be directly applied to the. treatment of special screens.