Principles of power-frequency magnetic shielding with finite-width plates

Abstract

SUMMARY Shielding principles are essential for guiding the efficient design of effective shields. In this paper, equivalent magnetic dipoles are first introduced to discuss shielding mechanism and characteristics of finite‐width metal plates. It is found that the magnetic field contributed by a plate decays with 1/r2 or 1/r3 generally. Magnetic shielding is effective if both equivalent and source dipoles have the same orientation. Such shielding retains even at infinity. Shielding is ineffective if their orientations are different. In such a case, an edge effect is observed no matter what material the plate is made of. The edge effect of conducting plates can be eliminated if two connected plates are placed around the source. Shielding against a monopole source is observed in the near region, even with a conductive plate. Monopole‐source shielding with a ferromagnetic plate is almost the same as dipole‐source shielding under orthogonal dipole orientations. Impact of other parameters, such as plate location, size and material, is addressed and interpreted physically using the equivalent dipoles. Copyright © 2013 John Wiley & Sons, Ltd.

A Stable Extended FDTD Thin-Wire Model for Lossy Wire Structures With Irregular Cross Sections

“…In a conductor made of linear magnetic material, the inductive contribution resulting from magnetic polarization has to be included in the voltage equation. According to the constitutive equation for a linear magnetic material, the following matrix equation in terms of element current density ( 𝑱 𝑐 ) and magnetization vector ( 𝑴 𝑥 and 𝑴 𝑦 ) is established [26][27] where 𝑬 is a unit diagonal matrix, 𝐾 𝑒 = 1 𝜎 ⁄ and 𝐾 𝑚 = 𝜇 0 𝜇 𝑟 (𝜇 𝑟 − 1) ⁄ . By performing elementary operations similar to those in Section III, the voltage drop on a unitlength conductor, ∆𝑉 , can be derived.…”

Analytical Shielding Metrics-Based Shielding Configuration Guideline for ELF Magnetic Field Mitigation

“…The reflection coefficient can explain the effect of shielding materials in the current source region, and the geometrical shielding effectiveness compensates for the weakness of the conventional shielding effectiveness, which cannot exactly describe the effect of the increase in the thickness of the shielding material. The solution of the Helmholtz equations in all regions is obtained by extending the approach of conventional research [13], without distinguishing whether the shielding material is a good conductor. In Section III, using these metrics, a detailed parametric analysis of the geometrical and electrical parameters of shielding materials is performed.…”