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Re: space winding
Hi all,
I have a question as to this 'proximity effect'?
As I understand it, the effect comes about due to the field generated
by the wire affecting the adjacent wire. Now, considering that the
high current carrying part of the coil is the lower, say third, of the
secondary, would there be any advantage in spacewinding the lowest
quarter, or third of the secondary and then going closewound for the
rest. I assume someone would have done this, is there any quantitative,
(qualitative - bigger/brighter sparks :-) ), results to this method?
As for turn-to-turn arcing, I too had some problem with this but it was
eliminated after carefully fine tuning the coil. While I was doing this I
noticed that when out of tune, I suffered turn to turn arcs near the lowest
part of the coil and racing arcs from near the top - as one would expect,
here's the intersting part, as I varied the tuning, (higher/lower FrP)
the distance from the top and bottom of the secondary where these problems
would
occur varied also. It seemed to me, correct me if I'm wrong, that as I
decreased
FrP, the burn/breakout effect would move towards the ends of the coil. If I
went
too far, the effect would appear near the center of the coil, and I would
have to
go 'back' with my primary tap. I have a mental idea/image why this is but am
asking the list if there is a definitive reason for this effect?
BTW - totally 'smoked' a secondary doing this, but learned heaps!!!
Best Regards all
Robin
Tesla list wrote:
> Original poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net>
>
> 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.