Re: Using skin effect

Subject:       Re: Using skin effect
       Date:   Tue, 22 Apr 1997 08:03:26 +1200
       From:   "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization:  Wellington Polytechnic, NZ
         To:   tesla-at-pupman-dot-com

HI Alfred, all,
                One skin depth in copper is 66/SQRT(f) mm. The 
definition of a skin depth is that distance inwards to the point 
where current has dropped to 1/e of its total value. The equation 
above has resistivity factored in so will be different for silver.
In fact, the skin depth on silver is not as deep due to the higher 
conductivity. If a silver film is not thick enough I have heard
things could actually be worse than bare copper. And it stilll 
requires enough conducting cross-sectional area to carry the current 
without significant heating (resistance).


 > Date forwarded: 
Sun, 20 Apr 1997 
22:38:33 - 0600 > Date sent:      Mon, 21 Apr 1997 00:18:23 -0500
> To:             tesla-at-poodle.pupman-dot-com
> Subject:        Using skin effect
> Forwarded by:   tesla-at-pupman-dot-com
> From:           Tesla List <tesla-at-pupman-dot-com>

> Subject:  Using skin effect
>   Date:   Sun, 20 Apr 1997 18:19:27 +0500
>   From:  "Alfred A. Skrocki" <alfred.skrocki-at-cybernetworking-dot-com>
>     To:   Tesla List <tesla-at-pupman-dot-com>
> At the frequencies we are using most of the current flowing through 
> the primary windings should be in the outer most layer of the 
> conductors (skin effect). Has anyone compared the performance of a 
> copper tubing primary to a silver plated copper tubing primary. It 
> would require a heavy silver plating to insure that all conduction 
> was going through the silver and not the copper. In theory if all of 
> our primary currents are traveling only through the outer few mills 
> of the conductors we may be able to use silver plated plastic tubing 
> (maybe garden hose for really large coils) for inexpensive primaries 
> that may very well yield better efficiency's than copper tubing and 
> be a heck of a lot easier to work as well! BTW does anyone know of 
> any equation to calculate the depth of conduction for a given 
> frequency, I vaguely remember seeing a formula for calculating the 
> depth of skin effect for a given frequency. This would expedite the 
> determination of what thickness the plating should be.
>                                Sincerely
>                                 \\\|///
>                               \\  ~ ~  //
>                                (  -at- -at-  )
>                         -----o00o-(_)-o00o-----
>                            Alfred A. Skrocki
>                    alfred.skrocki-at-cybernetworking-dot-com
>                              .ooo0   0ooo.
>                         -----(   )---(   )-----
>                               \ (     ) /
>                                \_)   (_/