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Re: Ah, thanks.

Tom Dawson: ""Are you suggesting that people are widely misinformed, or that, instead, perhaps the equation is only slightly inaccurate under these conditions? ""

Misinformed is a bit harsh, however, that is essentially correct.

The development of skin depth equations makes the assumption that the radius of the conductor is large with respect to the calculated depth. This means that for small wires, the equation incorrectly calculates the depth as too deep.

The better websites will provide that caveat that the equation is not accurate for wires that are 5 to 8 times the depth.

The fact that multiple websites provide the same formula does not necessarily mean it is correct.

From what I recall, the difference between the exact solution and the exponential approximation for a wire of about 14 guage with 20Khz applied, was about 4 to 1...meaning the exponential approximation gave a skin depth that was almost 4 times too shallow.

Going to smaller wire at the same frequency only makes the error worse, as the wire radius compounds the error.

Cheers, John


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