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Re: space winding
Hi David,
Tesla list wrote:
>
> 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.
David, as you know, I can attest to your coil performing "outstandingly"! Quite
a site to see! I did a few calcs on your coil. First using your 16 ga., then
with 20 ga. There was little change to reactance, DC ohms, primary tune point,
etc... For 20 ga., I used a double coated magnet wire value and added a spacing
value of 0.023" to get the number of turns near what you use now. Note the
spacing of .023" fits well within the 50 to 100% spacing as John F. preluded to
(bare wire of 20 ga. is 0.032").
I think it's quite possible that secondary losses due to proximity effects can
be reduced by space winding the coil. However, I'm not sure that at high power
levels, one could ever tell the difference as the gap will be the main show for
losses. I think you coil could have wound it with the 20 ga. wire and it would
have performed just as well, and possibly with a slight decrease in power
required to achieve the arc lengths you are now getting (not sure how
measurable the difference would be).
What may show a difference is a closewound 16 ga. to a closewound 20 ga. One
would expect the 20 ga. to out-perform the 16 ga. because the primary
inductance increase required on 20 ga. coil would reduce gap losses outweighing
any proximity losses in the secondary's. So, betweeen these two later
comparison's, the 20 ga. would be a better design (or would it?). High powered
pig coils that are truely run at least to their rating may not show the
expected results as cap values are typically larger resulting in a bigger bang
at the gap and possibly larger losses would follow (that would be interesting
to find out).
Take care,
Bart
Note a
>
> 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.
>
> I'm not good at the technical aspects of coiling, I'm just going by what
> I have seen. And I'll admit that max efficiency has not been a top priority
> in my coil designs, just to get the biggest sparks that I possibly could
> by hook or crook. I'll bet there's a few other coilers like that. too.
> Please, Malclom, John, or any other knowledgable person on the list,
> feel free to further comment on this thread, as I want to learn all that
> I can regarding this.
>
> David R.