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Mysterious result....
I have been running a 4.5in O.D. by 24in coil now for some time. My primary
had been designed for a larger coil its' dimensions are: 10in I.D., 30in
O.D. 12 turns 3/8 copper tube tapped at 10 turns, saucer shaped helix 30
degrees incline. Cap value of aprox .01mf. My supply is a 15kv 60ma neon
and I was running a series gap of 8 lengths copper pipe with 1/16in spacing
for a total of 1/2in gap. After repeated trials I was never able to get the
gap to fire consistently using more that 6 gaps (3/8in total). At seven
gaps, the the fireing would be intermittent or would cease altogether after a
time. With 8 gaps (1/3in) the gaps would not fire at all even with full
turn-on surge (no variac)
I was always curious as to why this was the case. It would seem to me that a
1/2in gap shouldn't be to large for a 15kv/60 neon to bridge but I never
pursued the details since the coil seemed to run just fine at 3/8in and I
suspected that it would be gentler on my cap anyway.
Here's the strange part. I recently switched to a smaller primary: 6in I.D.
- 18in O.D. with 12 turns 3/8 copper tube banked at 45 degrees. This
produced much greater output - due to increased coupling characteristics I
would guess. I also found that I could now run at the full 8 gap (1/2in)
setting on my gaps without any intermittency noticeable. The local expert
was stumped as to why this might be the case.
The only potential explanation I could come up with is that due to the
increase in coupling, the back EMF pulse (as the secondary waveform
collapses) is sufficient to bridge the extra gaps and keep the gap system
fireing when it otherwise would not (was not).
Any ideas out there?
Thanks in advance:
-DavidF-