skäreffekt

The skäreffekt, also known as the edge effect, is a phenomenon observed in the behavior of alternating electric currents flowing through conductors. When an AC current passes through a conductor, it tends to concentrate towards the outer surface of the conductor rather than being uniformly distributed throughout its cross-section. This effect becomes more pronounced as the frequency of the alternating current increases.

The skäreffekt is a consequence of Faraday's law of induction. The changing magnetic field generated by the alternating current induces eddy currents within the conductor itself. These eddy currents oppose the change in magnetic flux, and their induced magnetic fields tend to push the main current towards the conductor's surface where the magnetic flux is weakest. This effectively reduces the usable cross-sectional area of the conductor for carrying current, leading to an increase in its effective resistance.

At lower frequencies, the skäreffekt is negligible, and the current distribution is nearly uniform. However, as the frequency rises, the eddy currents become stronger, and the current becomes increasingly confined to a thin layer near the surface. The thickness of this layer is known as the skin depth, which is inversely proportional to the square root of the frequency and the conductor's permeability and conductivity.

The skäreffekt has significant implications in electrical engineering. For instance, in high-frequency applications like radio transmission or power transmission at very high voltages, conductors are often designed with hollow cores or by using multiple thin wires (litz wire) instead of a single solid conductor to mitigate the increased resistance and power losses caused by the skäreffekt.