Re: strap primaries

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

"better" in what terms?  If you are trying to save weight (or cost) of
copper, or need a better structural form, etc. then strap is probably the
lowest RF resistance per unit weight or volume.

Corona problems come from the small radius of curvature on the edge of the
strap.  If you were using 1/8" copper bars, and round the edges, it's not
such a big issue, although, you'd have to watch the neighboring objects and
fields. At a radius of 1/16" inch, breakdown voltage around 71/16 or 4 kV.  

Compare nominal 1/4" copper tubing (OD is actually 0.375"), for which the
breakdown field would occur at around 13kV.

But, since copper tubing comes from the store nicely bent in coils already,
it's a fast and easy manufacturing process.


Tesla list wrote:
> 
> Original poster: "Mr Gregory Peters by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>
> 
> Hey guys, A question about primaries.
> 
> I once read that copper strap has better RF conductive properties than
> copper tube, but we use tube in tesla primaries to suppress corona
> loss. My question is why? If you have, say, a peak primary voltage of
> 40kV and a 10 turn primary, don't you technically only have 4kV/turn?
> Isn't 4kV too low a voltage for corona discharge to really be a
> problem? I would rather use strap as it is much easier to bend then
> tube.
> 
> Cheers,
> 
> Greg Peters
> Department of Earth Sciences,
> University of Queensland, Australia
> Phone: 0402 841 677
> http://www.geocities-dot-com/gregjpeters