Shielding Effectiveness of a Double-Shell Non-Magnetic Conducting Cylinder Rotating in an External Transverse Low-Frequency Magnetic Field: An Analytical Approach

This letter deals with the problems arising from the low-frequency magnetic field surrounding the rotating double-shell non-magnetic conducting cylinder, in which the shells may have different electrical conductivities and thicknesses. Particular attention is paid to the magnetic field inside the cylinder. General closed-form analytical expressions for the shielding effectiveness are given, assuming that the shells can be treated as “electromagnetically thin.” In fact, “thin” means that the shells can be of any thickness, but must be thinner or at most comparable to the diffusion skin depth, which is not a particularly high requirement in practical arrangements. A comparison with the results obtained using the finite-element method for the real physical dimensions of the shells are presented. It is obvious that numerical solutions have more possibilities than analytical ones. Nevertheless, analytical solutions provide general insights which cannot easily be extracted from numerical procedures and are useful for a qualitative presentation of the role of various system parameters. The output of this letter can be applied to optimization of the design of a double-shell cylindrical shield.