Re: A new mini-coil competition winner!

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: FutureT@xxxxxxx 

In a message dated 6/6/06 7:45:43 PM Eastern Daylight Time, 
tesla@xxxxxxxxxx writes:


> Also, did you see any reason ScanTesla predicted only 6.4" streamers?
> >My earlier post contained the input and and output files I used in
> >the program.


Karl,

Congratulations on your results.   It's a great looking coil
too.  I think the coil may be drawing more than 47 watts.
If the output voltage is figured at 4.4kv rms, that comes
to 155VA output.  Figuring 155 watts wallplug, and
using my formula of

  spark length inches = 1.7*sqrt input power watts

gives 21" as a spark length.  So it seems
to me that your coil is working well.  Most
small coils fall somewhat short of my formula.
Your break rate must be higher than 120 bps because
of the use of a resonant value
capacitor.  Maybe the firing voltage is a little higher
than expected for some reason. The large radius of
curvature of your topload
may be helping the results also, even with the breakout
point.  Also I agree with Gary that the high primary
inductance is probably reducing the gap losses and
helping the results.  Your spark length at 18" is
close to the value of 21" which my formula "predicts"
If the power input is as I suggested.
The higher breakrate is probably reducing the efficiency
some also, but apparently not much.  Regarding gap
losses, I think that the initial energy transfer to the
secondary is what contributes most to the spark length.
The initial transfer tends to involve rather low gap losses
especially when using a high inductance primary.

I once built a coil which was similar in physical size.
It used a 3" diameter by 15" tall secondary with a 3"
x 10" toroid.  It was the TT-32 coil.  It used a 7.5/30
NST and drew about 270 watts I think.  So the predicted
spark length was 28" but it only gave about 25" sparks.
I used a 120 bps rotary gap however.

John