Terry's Little SISG Research Coil

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Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

Long long ago, in a time I forgot,...  I started working on a "little 
research" Tesla coil...  A very simple, reliable, repeatable, solid 
state thing...  Big sparks were not the issue, but rather a coil 
always "ready to go" in any situation.  No lost cables, damaged 
secondaries, blown parts...

Well, the SISG was made to run it, which was like a four month 
"delay" :o)))  It's parameters are probably more accurate and better 
known than any coil on Earth ;-))  It's output is deliberately 
"limited" so scopes, test equipment, and computers can be near it.

A paper describing it is here:

http://drsstc.com/~sisg/files/SISG-coil/SmallSISGCoil.pdf

Forgive if it is "technical"...  This is a VERY "technical" coil...

It runs rock solid and is totally repeatable, even if I go back and 
measure the parameters after long running.  No other coil I have 
every had has been totally "repeatable"...

It is an "odd" thing...  It runs at 120, 240, 360 , more... BPS 
depending on the variac setting (as designed ;-))  But the "gap is 
"silent" (Well, you can hear the magneto constriction if you try) and 
the running is "perfect".  It does not sputter, hiss, or vary.  It 
runs almost like a DRSSTC but no electronic "brains"...  I actually 
seems far more "stable" than my DRSSTC...  It is super cool for 
corona stuff!!  Peak voltage is 139kV, and yes, it really IS that 
accurate!!!  I suspect much of the seeming stability is due to it 
being pretty lower voltage.

It will not breakout without a "point".  Cool for many tests...  But 
if you were wanting a "real" coil, just add another MOT to double the 
voltage >:-)))  Higher bridge PIV too... But "I" kept it tame with 
just one MOT so I would not blow it up like I have all my "other" 
research coils :O))

It is pretty "cheap"!!  I just used SISG boards I had as scrap.  Just 
very common stuff and four CD caps...  I spent ~$75 on stuff for it 
mostly the Lexan, odd parts, and pretty woodwork ;-))  There is not a 
lot in there:

http://drsstc.com/~sisg/files/SISG-coil/P7150184.JPG    (big file)

I should note three things I found of note...

1.  The secondary coil was not effected at all in any measurable way 
buy the massive MOT nearby.

2.  The secondary has a "Q" of  213 and an AC resistance of 147.6 
ohms which is vastly "better" than all the programs predict...  I 
don't know why...  I have measured that in several ways now and my 
measured numbers hold solid and the separate types of measurements 
agree to 5%.  Maybe I just made it special good ;-))

http://drsstc.com/~sisg/files/SISG-coil/LittleWinder.pdf

3.  The primary resistance is 0.155 ohms.  0.06 ohms of that is the 
SISG.  I used 12 gage stranded wire for the hookups in very short 
lengths and big brass for the connections...  But there is 0.095 ohms 
in the primary coil and wiring.  Not a big deal, but 
"significant"...  The SISG stuff places new demands on primary 
resistance.  A conventional spark gap at 3 ohms would render the 
primary's "Q" at about "1" so it would not even run :o))))

http://drsstc.com/~sisg/files/SISG-coil/SISG-TPtest-FollowUp.pdf

Losses are:

Coil Power		53.1 watts
SISG			9.55 watts
Primary Loop R	15.12 watts
Secondary Rac	2.4 watts
Arc			25.9 watts

If I could quench on the first notch (11.2uS), this changes to:

Coil Power		53.1 watts
SISG			6.89 watts
Primary Loop R	10.9 watts
Secondary Rac	2.88 watts
Arc			30.8 watts

I looked into quenching by careful selection of R4 on the 
SISG.  However, the voltage drop at the gate and the currents 
required per time did not add up.  The e^-t/RC curve does not have 
the drive at the right times to quench but still sustain the "good" 
currents.  At higher currents, a low R4 (like 60 ohms) just will not 
work for fast quenching :-(  It will take more "electronics"...

So that is what I have been doing this last six(!!) months...

Cheers,

	Terry