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Re: Using skin effect
Subject: Re: Using skin effect
Date: Sat, 3 May 1997 22:34:17 +0500
From: "Alfred A. Skrocki" <alfred.skrocki-at-cybernetworking-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
On Mon, 28 Apr 1997 20:18:06 -0700 Bert Hickman
<bert.hickman-at-aquila-dot-com> wrote;
> All,
>
> Alas, the perils of an early morning post! The above gives the factor
> (x) of AC resistance divided by DC resistance, not skin depth! Sorry
> 'bout that!
>
> Skin depth = 1/SQRT(Pi*f*Uo*a) for a cylindrical conductor (meters)
> where f = Hertz
> Uo = 4*pi*10-7 Henry/meter
> a = 5.80x10^7 mho/m (conductivity of copper)
> = 6.17x10^7 mho/m (conductivity of silver)
>
> Copper skin depth = 66.1/SQRT(f) millimeters
> = 2602/SQRT(f) mils
>
> Silver skin depth = 64.1/SQRT(f) millimeters
> = 2523/SQRT(f) mils
>
> Comparing skin depths (in mils = 0.001") of the two metals at various
> frequencies:
> Skin Depth (mils)
> f Silver Copper
> ====== ====== ======
> 10 kHz 25.2 26.0
> 50 kHz 11.3 11.6
> 75 kHz 9.2 9.5
> 100 kHz 8.0 8.2
> 200 kHz 5.6 5.8
> 300 kHz 4.6 4.8
> 400 kHz 4.0 4.1
> 500 kHz 3.6 3.7
> 750 kHz 2.9 3.0
> 1000 kHz 2.5 2.6
>
> As can be seen, copper tubing is very hard to beat! At typical Tesla
> Coil frequencies, smooth copper tubing is almost as good as it gets!
> Only pure silver or relatively thick silver plating can beat it.
Interesting equation Bert, where did you get it from?
Sincerely
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Alfred A. Skrocki
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