Magnetic shielding by ferromagnetic trunking in low-voltage installations

摘要

Galvanized iron (GI) trunking used for mechanical protection in low-voltage electrical installations has demonstrated some degree of magnetic shielding. This paper investigates extremely-low frequency magnetic shielding by commercial GI trunking based on numerical analysis and experimental studies. First general shielding characteristics are discussed where the shielding material is considered linear. Since galvanized iron is a ferromagnetic material, and exhibits non-linear properties associated with its permeability, the variation in shielding performance resulting from the nonlinearity is then discussed. The shielding impact of both source and shield parameters associated with ferromagnetic trunking is determined. It is concluded that galvanized iron trunking is a cost-effective shielding measure for LV electrical installations in buildings if properly designed and installed.