Skin effect

Definition of skin effect, its causes and its solutions are discussed in this presentation.

1. Ch.M. Ilyas Ghumman UOG

2. What is Skin Effect? Skin effect  is the tendency of an  alternating electric current  (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor.

3. Skin Effect

4. Skin Depth(δ) S kin depth  is a measure of the depth at which the current density falls to  1/e  of its value near the surface S kin depth also describes the exponential decay of the electric and magnetic fields, as well as the density of induced currents Distribution of current flow in a cylindrical conductor , For alternating current, most ( 63%) of the electric current flows between the surface and the skin depth ( δ )

5. Factors Effecting δ Frequency of the current and the E lectrical and magnetic properties of the conductor

6. How Skin Effect Produces? The skin effect is due to opposing  eddy currents  induced by the changing  magnetic  field resulting from the alternating current . Skin depth is due to the circulating eddy currents (arising from a changing H field) cancelling the current flow in the center of a conductor and reinforcing it in the skin

7. Skin Effect At 60 Hz  in copper, the skin depth is about 0.65 um . Due to the skin effect AC resistance increases in conductor At high frequencies the skin depth becomes much smaller.

8. How to Overcome Skin Effect? Using good conductor Decreasing Frequency

9. How to Overcome Skin Effect? By Using bundle of Conductors By using Litz Wire

10. Formula For Skin Depth We can derive a practical formula for skin depth as follows where = resistivity of the conductor = angular frequency = relative magnetic permeability of the conductor = the permeability of free space

11. Example to Find δ And for 60 Hz Skin Depth is 10.1 mm for Gold Gold is a good conductor with a resistivity of 2.44×10 −8   Ω·m and is essentially nonmagnetic: 1, so its skin depth at a frequency of 50 Hz is given by