Re: AWG vs. Diameter

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Terry -

This is kind of interesting to look at. (150kHz with Sd of 0.0067"). At
this rf and
depth, would the wire then be electrically equivalent to a wire size of
0.0067 with
the associated resistivity of that wire size? (got a feeling the answer is
mostly
no). But if so, my primary would equate to around 22 ohms during while
ringing at
150kHz. Sd in itself would be an interesting study.

Take care,
Bart

Tesla list wrote:

> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>
> Hi Chris,
>
> A complex question :-))
>
> Due to skin effect, RF currents only travel on the outer layer of wire.  For
> copper, that thickness in inches is:
>
> D = 2.602 / SQRT(F)
>
> So at 150 kHz, the thickness of the layer of current flow is only 0.00672
> inches.  You could use very thin copper tubing indeed without noticeable
> effect.  Taking the skin depth into account and doing the math to find the
> conductive area of each conductor:
>
> 1/4 inch tube = 0.0051345 square inches
> #6 wire = 0.00327 square inches.
>
> So the tubing has 57% more conductive area that the wire.
>
> However, let's consider the coupling.  Using Dr. Rzeszotarski's program on a
> coil with dimension just like mine...
>
> 1/4 tubing = 0.198
> #6 = 0.196
>
> So the wire has slightly less coupling, but nothing to worry about.
>
> Then, as the recent discursion about the inner turns getting hot showed, we
> have to consider proximity and eddy current effects.  Unfortunately, I don't
> have an answer there.  I would think the thinner wire would be better, but I
> don't really know.
>
> In general, people tend to find that the thicker tubing does better than
> thinner wire.  We always attributed that to the differences in skin depth but
> these new proximity and eddy current factors may matter a lot too.  Primary
> losses can really eat up a coil's performance so this is pretty critical
stuff.
>
> Cheers,
>
>         Terry
>
> At 06:18 PM 3/16/2002 -0500, you wrote:
> >
> > Hi Folks!
> >
> > Can anyone tell me the difference between 1/4" copper tubing and say, 6ga
> > wire? How do they compare in current carrying capability? Just curious
> >
> > Chris W