Low-frequency skin effect in Aluminum conductors: Theory, simulation, and experiment

Abstract

Electromagnetic field propagation in conductive media and the resulting skin effect are basis to the analysis of power systems, electromagnetic shielding, and signal transmission. Although classical electromagnetic theory accurately describes skin depth and its dependence on material properties and frequency, experimental investigation at very low frequencies remains challenging. In good conductors such as aluminum, the skin depth at power-line frequencies is comparable to typical conductor dimensions, leading to weak attenuation and an almost uniform current distribution. In this study, the skin depth of aluminum at 50 Hz was investigated using a combined theoretical, numerical, and experimental approach. Analytical expressions for the attenuation constant and skin depth were derived from Maxwell’s equations for a linear, isotropic conducting medium, yielding a theoretical skin depth of approximately 11.60 mm at 50 Hz. Numerical simulations were performed in the frequency domain using COMSOL Multiphysics 5.5 to investigate the current density distribution and the frequency-dependent behavior of the skin effect, showing a nearly uniform current distribution in a 10 mm-radius aluminum wire at 50 Hz and a prominent skin effect at higher frequencies. Experimental measurements were carried out using aluminum sheets of varying thickness, and the attenuation of the electric field amplitude was analyzed to estimate the experimental skin depth. The experimentally obtained value, approximately 36.6 mm, was larger than the theoretical prediction. This discrepancy is attributed to finite sample geometry, edge effects, measurement uncertainty, and deviations from ideal material assumptions. The results highlight the limitations of low-frequency skin depth measurements and provide insight into the factors governing electromagnetic field behavior in conductive media under practical laboratory conditions.