The document discusses the skin effect phenomenon in conductors carrying alternating current. It defines skin effect as the tendency of AC to flow mostly near the surface of a conductor. It then defines and explains skin depth - the depth at which current density decreases to 1/e of its surface value - and how it depends on frequency, resistivity, and permeability. Factors like eddy currents induced by the changing magnetic field are said to cause the skin effect. The document also provides formulas to calculate skin depth and gives an example using gold at 60 Hz.

2. Ch.M. Ilyas Ghumman
UOG

3. 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.

4. Skin Effect

5. Skin Depth(δ)
• Skin depth is a measure of the depth at which the current density
falls to 1/e of its value near the surface
• Skin 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)

6. Factors Effecting δ
• Frequency of the current and the
• Electrical and magnetic properties of the conductor

7. 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

8. 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.

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

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

11. 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

12. 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