Re: space winding

["Malcolm Watts" <M.J.Watts-at-massey.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Dave,
         Proximity effect is a close relative of skin effect.
Magnetic fields tend to reduce the effective cross-sectional 
area of the wire. One of the best discussions I've seen on 
this is a paper by Philips on winding power inductors for 
switchmode power supplies. They lay the issues out in detail.
Like I said though, this doesn't contradict the results you've 
been getting because you'd still have a secondary Q well in 
excess of a hundred (i.e. negligible conduction losses in the 
wire). Poor results only show up when the secondary losses get 
pretty bad relative to the primary. It's just that I'd rather 
pay a lot less for wire and have a lighter coil to boot for 
the same results.

Regards,
malcolm


On 8 Aug 00, at 16:29, Tesla list wrote:

> Original poster: Tesla729-at-cs-dot-com 
> 
> In a message dated 8/8/00 11:52:45 AM Pacific Daylight Time,
tesla-at-pupman-dot-com 
> writes:
> 
> << What I found was that a closewind with 
>  heavier gauge wire just costs more in wire because any benefit 
>  the heavier gauge gives is knocked flat by the proximity 
>  effect when the turns are in closest proximity to one another. >>
>  
> Malcolm, John F,
> 
> Well, I guess the verdict is in, then. Both of you
> have pretty much answered with almost identical comments 
> about the "proximity effect" of minimal spacing of windings. I
> am a little confused though, as my present largest coil system,
> "Medusa" has a close-wound sec coil and its performance, to
> me at least, is outstanding. I have had to get a few bugs out
> of the system as far as turn/turn flashovers, but now it produces
> down right frightening discharges with my 10 KVA pole pig pow-
> er source with no problems. It's sec is close-wound with #16
> double-coated magnet wire and the sec dimensions are 12" dia
> x 38" long ( ~665 turns). With an 8" x 32" toroid top load, I get 8
> to 10 ft. sparks in a claustrophobic (hope I spelled that right) 12'
> x 20' shop -at- 7 to 8 KVA. If I run it maxed out, (around 11 KVA) 
> the sparks don't have room to grow in length, they just get bright-
> er, fatter, and louder. Of course, I DO use a rotory spark gap and
> a 0.0825 uFD tank capacitor. Anyway, this is the best perform-
> ance that I have ever obtained to date and I'm already quite cramped
> for space by the sparks that I have now, so until I can get into larger
> facilities, I won't be trying to get any bigger with my sparks. I forgot
> to mention that the primary coil's L is ~32 uH. I won't go into any
> more detail of my system right now as the turn/turn spacing was
> the issue -at- hand.

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