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The first part of this article is a descriptive discussion of magnetic shielding in general. Formulae are then given for the calculation of shielding efficiency of cylindrical shells for steady and alternating magnetic fields. By means of these formulae the shielding efficiency for various types of cylindrical shields has been calculated for a steady magnetic field. The second part of the article contains experimental information on various types of transformer shields. This information supplements the theory in connection with factors which would be very laborious to treat theoretically. The theory and the experimental data are coordinated in such a manner that the shielding efficiency of a particular shield can be calculated with an accuracy which is sufficient for practical purposes.
W. G. Gustafson (1938) studied this question.