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Re: surface area of wire + thoughts



Original poster: "chris swinson" <exxos-at-cps-games.co.uk> 

Hi all,

I've been wondering  about the stranded wire coil giving better results.
Since SSTC tuning is crytical I wonder if the larger self C coils work less
becasue when the arc forms it will de-tune it. I tested the coils a long
time ago and the very small coil with 0.2mm wire de-tunes very easily (
though it does give good results ) I only need to place my hand within 3foot
of the coil and the spark vanishes. With the multistrand coil the turns are
much further apart and I have to place me hand on the coil itself to get any
effect on spark output. I wonder if this is the reason to why my standed
coil works better than my solid core 1.6mm coil. I'm still not 100% happy
with explination, im sure the Q will be higher with stranded wire, but maybe
less since the turns are spaced out.

I did construct 4 coils with different types of wire, I tried to keep the
length of wire the same in each case though in each case thicker wire gave
1" less spark each time. I can only put this down to the lower inductance.
The higher inductance coils draws more power from the SSTC thus gives better
results. Which is fine until I work with the stranded wire coil which has
much less inductance and gives good results when it shouldn't.

I can only roughly conclude that in some respects the coil is worse but in
other respects it is better than solid wire. But WHY is it ?

For example if my 0.2mm coilgives out 2" arcs with say 50VDc input -at- 1amp
( just example values here ) my 0.4mm wound coil has half the inductance and
draws half current from the SSTC, and thus gives 1" arc at 50VDC input 0.5A,
so my 0.8mm coil gives out 1/2inch arc, my 1.6mm has no output at all. This
makes sence though I even tried more turns on the primary to force mroe
power input and it had little effect.  The odd part now is that my
multistand coil has even lower inductance than the 1.6mm coil ( which gave
no output ), now the SSTC is providing even less current than the 1.6mm coil
and giving a arc 2inches long. I mean as good as it sounds I've just gained
like a 80% save input power with a coil which really shouldn't work at all.
I dont have exact figures to hand though I did document each test and repeat
it many times. I wish I had kept a diary on such tests rather than jotting
stuff down on scrap bits of paper, though the end result is how I described
it.

Anyone got any ideas on this, can the fact that its down to the multistrand
wire that the coil have been given a vast Q boost ?

Chris