Alternating Current Skin Effect and 50 vs 60 Hz

ruxton.stanislaw

Senior Member
Location
Arkansas
Occupation
Laboratory Engineer
The skin effect, in electrical terms, describes how AC (Alternating Current) tends to concentrate near the surface of a conductor as the frequency increases. This phenomenon becomes more pronounced at higher frequencies. Here's how it relates to 50 Hz vs 60 Hz and wire diameter:

Impact of Frequency:
  • 50 Hz vs 60 Hz: The difference between 50 Hz and 60 Hz is relatively small (10 Hz). At these low frequencies, the skin effect is not a significant factor for most commonly used wire sizes in building electrical systems.
Impact of Wire Diameter:
  • Larger Diameter: With a larger diameter wire, even at 50 Hz or 60 Hz, a significant portion of the current will still flow throughout the conductor's cross-section. The skin depth (the depth at which the current density falls to about 37% of its surface value) is larger for bigger wires.
The Takeaway:
  • In most residential and commercial electrical applications using standard wire sizes (say, 12 AWG to 2 AWG) at 50 Hz or 60 Hz, the skin effect is negligible. The current will be fairly evenly distributed across the entire conductor.
When Skin Effect Matters:
  • High Frequencies: The skin effect becomes a major concern at much higher frequencies, such as those used in radio waves and high-power electronics. In these cases, wire diameter selection becomes crucial to ensure efficient current flow and minimise power loss.
  • Large Diameter Conductors: Even at 50 Hz or 60 Hz, if you're dealing with very large diameter conductors (used in high-power transmission lines), the skin effect can become noticeable. Here, engineers might consider using special conductor designs like hollow cores or stranded wires to mitigate the effect.
For everyday electrical work with common wire sizes at power grid frequencies (50 Hz or 60 Hz), the skin effect is generally not a major design consideration.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
If conductors are sized using NEC tables, skin effect does not need to be considered at all.
I don't know why instructors would spend more than 5 minutes on the subject, when they are discussing lightning protection.
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
When Skin Effect Matters:
  • High Frequencies: The skin effect becomes a major concern at much higher frequencies, such as those used in radio waves and high-power electronics. In these cases, wire diameter selection becomes crucial to ensure efficient current flow and minimise power loss.
Another advantage of using paralleled smaller conductors.

That's where Litz wire comes in:

https://litzwire.com/litz-wire-design-engineering/

https://en.wikipedia.org/wiki/Litz_wire
 
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