Re: Optimal Quench & Update

        Re: Optimal Quench & Update
        Tue, 1 Apr 1997 14:23:11 -0500 (EST)

>>  I set up a small 360 VA (12kV, 30ma neon) coil for quench testing.
> > Steady
>> first notch quenching was achieved at k = .11, k = .12, and at k = .18,
> > spark length was 36".
> > 
> > Specs are as folllows;     Primary is #12 standed pvc ins, 15 degree
> > inverted
 >> cone, tapped at 33 turns  (448uH).  C = 0.007uF, polypropylene.
> > Secondary is
> > 6- 1/2" by 23" plastic form wound with #28 formvar, L = 108mH.  Resonant
> > frequency without toroid is 130 kHz, with toroid is probably about 100
> > kHz or
>> so.  Toroid is 4" by 17" aluminum dryer duct.  Gap is a 120 BPS
> > synchronous
> > 12 point super-series quench rotary (the spark snakes through 12 gaps
> > during
>> each firing).  There are 12 spinning and 12 stationary electrodes, all
> > electrodes are 1/8" dia. stainless steel.  Motor is 3600 rpm, 1/10 HP
> > salient
> > pole design with ~7" rotor.  Six of the gaps are "offset".  Maximum
> > voltage applied to the Tesla coil transformer is 125 volts.
> <SNIP>
> John,
> Great experiment! In order to hit k=.22 without self-destructing your
>secondary, you may need to use a relatively heavy overcoating of some
>type (Behr or similar). Also, its very interesting that you were seeing
> near-linear ringdown on the secondary - this may indicate that the power
> dissipation properties of heavily-conducting secondary streamers are
>similar to that observed in the primary circuit arc...
> Safe coilin' to you, John!
>-- Bert -- 
> <SNIP>
>> John Freau
Bert, All,

Yes, I was surprised (but glad) to see such a rapid ringdown, seemed to
good power transfer, maybe I just happened upon a good impedance match.  

I did a few more tests which I'll describe: 

First I went back and found the the magic k points that I had missed
and as expected, I was able to obtain first notch quench at these other
values.   Next, I jumpered across 6 of the 12 gaps to test the system
"poor" quenching conditions.  This caused quenching on the 3rd notch,
sparks were about 20 % weaker, but coil ran poorly and unsteadily.

Back to normal operation; one time at k = .15, with input voltage at 130
volts, I thought I saw the spark hit 42", but this happened only one
 In general, spark is longer at k = .12 because only one streamer is
the spark regularly reaches 38" with variac set at 130 volts.  

Next, I tried to achieve first notch quenching at k = .22, but the
failed, and 2nd notch quenching was obtained, along with racing sparks
caused some damage to the secondary.   Perhaps a slightly larger toroid
help the quenching by increasing the loading, and might also cause only
(longer) streamer to be formed.  I have also noticed that quenching is
with multiple streamers than with one long one.  At k = .22, the system
is a
real "Behr"!   : )

Towards optimal coiling, 

John Freau