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Re: Report on Scoping Work Coil
HI John, list,
Please note that I am not attempting to break records
etc. Simply trying to understand just what can be done if transformer
losses are left out of the equation. More below....
> Original Poster: FutureT-at-aol-dot-com
>
> In a message dated 99-12-08 14:35:05 EST, you write:
>
> << Original Poster: "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz>
>
> > Hi all,
> > I finally got around (and the guts) to scope my work coil
> >
> > running normally to see what its BPS is (special interest for Boris
> > and John Freau). Ep is around 3J max for this coil. snip
> > In general, BPS appeared to be 100. Sometimes, it appeared
> > to fire twice per 1/2 cycle, other times it appeared to miss a beat
> > (npi). snip
> > I looked for myself and sure
> > enough, the coil was reaching out and attaching all around. Max
> > strike distance was somewhere in excess of 3.5' regularly and over
> > 4' occasionally.
> > Even supposing that the scope was lying and the thing was
> > firing at 200BPS, that is still a primary power of around 600W for
> > 4'+. All this with a simple single 1/2" electrode W-C static gap.
> > Is anybody out there keen on duplicating this coil and conducting
> > their own investigation? I am restricted in both space and
> > opportunity to run it since I no longer own it.
>
> Hi Malcolm,
>
> Thanks for your important report. Your's is still the most
> "efficient" coil I've ever heard of if it's running near 100 bps,
> which it certainly appears to be doing. If it's running 200bps, then
> my best TC results are similar, but never at 240 bps, I always get
> best results at 120 bps for my coils. So the efficiency of your coil
> seems exceptional at either bps.
>
> (Note to new list members: I'm writing "efficiency" in quotes because
> I'm using it to mean spark length vs. cap watts.)
>
> Your intriguing TC efficiency results, which seem to exceed greatly
> any other TC, certainly deserve and demand that more work be done.
> Lack of space is an issue I'm plagued by also. I wonder if there's a
> particular aspect of your TC that gives it it's efficiency, or if it's
> due to a synergy among the components? I could gradually modify my TC
> to make it more like yours. For instance I could try a big oblate
> toroid, then a 10" by 40" space-wound secondary, etc. I'd have to
> build a special flat base, to keep the coil away from the ceiling,
> etc. I'll see what I can do. Wouldn't it be nice if a coiler, who
> has plenty of space, etc, would jump quickly at this opportunity to
> explore and discover.
It is definitely synergetic. Pure luck really. I bought an offcut of
drainpipe, designed a coil on the back of an envelope around the
the former, decided to spacewind based on having two reels of
0.56mm wire available (bifilar wind with one removed after winding),
then decided to stick with the 0.1uF I'd been using with the
transformer to date. Decided on a helical primary, built the coil, then
retrospectively measured it to find out what was happening. This was
back in '93.
The transformer is losing a lot of power. It gets hot very quickly.
It is physically quite small so the heating is great. It may be that
larger transformers lose similar amounts of power but don't get hot
so quickly due to their size. I estimate it is consuming somewhere
between 500W and 1kW.
In order to get the voltage up using the 10k turn secondary, I
wound a 450t primary and used that in place of the 500t primary.
This increased Imag from about 1A to around 6A so the core is
running close to saturation. Measurements on it suggest that Cp is
LTR. Output over the 500t primary shot up radically.
Having finally got it firing reasonably well with the higher Xp
primary and larger terminal, my next move is to wind another
transformer using the 500t primary. Goals: reduce Imag to a
reasonable level to reduce core losses, use thicker wire for the
secondary to reduce I^2R losses and double Ep by using a higher
turns ratio. The hardest part of duplicating this system would be
duplicating the transformer. Reinhard take note: the transformer is a
demountable laboratory type made by Leybolds of Germany. Its
availability for use with this coil was pure serendipity. I used it on a
horrible desktop model for ten years before building this beast. I am
amazed to be getting around 3x the original sparklength using the
hotter primary and same Ep. It is obvious that efficiency tracks
physical coil size.
The new transformer secondary winding is under way but won't
be completed until sometime next year (only another 50 layers to go).
I am making better use of the winding window but breaking the rules
as far as interlayer creepage distance goes. The windings extend to
the edge of the bobbin. Ultimately, the goal is to find out what might
be done with best efficiency from the wallplug. I once arbitrarily
picked 10' from 2.3kW (230V, 10A outlet) as a nice goal to shoot
for. It might just be on. We'll see.
Regards,
Malcolm