[TCML] First (or maybe 2nd) light on my medium-sized SG coil

["David Rieben" <drieben@xxxxxxxxxxx>]

Hi all,

I have finally gotten my mid-sized SG coil project up and running
A quick rough-up of the specs are about 28" of #22 AWG magnet
wire wound on a 6" ID (6.5" OD) white PVC pipe for the secondary 
coil. The primary is 11 turns of 3/8" copper tubing wound in the 
classic Archemdian spiral with between 3/8" and 1/2" spacing be-
tween each turn and the outermost turn has about a 12.5" radius
(25"diameter). After initial tuning, the primary has been tapped at
approx. 8 3/4 turns. The transformer is a 120:1 GE potential trans-
former (14,400 volt output). Ballasting was origianlly going to be via 
a surplus saturable reactor that was rated at 12 kVA and was origi-
nally designed to run a bombarder and thus control 240 volts. Naturally,
I assumed that it shouldn't have any trouble holding the reigns on
120 volts input to a PT. However, it seemd that I was having a fer-
roresonant issue with the saturable reactor in this setup and I was
pretty quickly tripping the 20 amp panel breaker with only about
50 on the dial of the 22 amp Staco variac. The variac would also
start to make that heaving and humming sound with the start of 
the SG firing, like it was almost dead shorting. 

So I removed the sat-reactor and replaced it with (2) MOTs with
their seconadries shorted and their primaries in parallel to each 
other and of course in series with the 120 volt input to the PT. 
This does seem to offer better current control although it still seems 
to start rocking with Staco variac set at 50 to 60 on the dial (very fre-
quent 50 to 60" strikes to my tool cabinet in the garage). The MOTs 
do tend to get warm pretty quickly running like this though and I haven't 
had a chance to pull it outside to "pull the ears back on her" since I am 
confined for space inside of my garage and the arcs start hitting the ceiling
if I try to go beyond this (fire hazard, already been there, done that) < :^O
I don't have any metering on this coil's control panel and the Staco
variac IS the control panel at this time. Therefore I'm not really sure
just how much current that it is pulling but I can tell that it is up 
there a bit. I have at least stopped tripping the 20 amps panel
breaker since replacing the sat-reactor with the MOTs, though.

O yea, I forgot to mention that the SG is a simple stationary RQ 
style copper tube gap with (8) 1" diameter x 6" long copper pipe
segments and the resultant 7 gaps each spaced by the thickness
of a credit card. The primary cap is (2) paralleled RFI recon mica 
pulse capacitors, each rated at 0.04 uFd @ 40 kV for a total pri-
mary C of 0.08 uFd. The topload is a homemade 6" x 30" toroid
made from two 8 ft. lengths (when fully streched out) of 6" dryer
duct. Because of the relatively large primary C, I have found that 
the output is smoother when I short about 2 of the 7 gaps in the
RQ stationary SG. The gap will start "spitting" with the variac
is turned to around 30 on the dial instead of 45 or 50 and it makes
for smoother operation. I almost forgot to mention the the stationary
SG is forced air cooled by a pretty robust fan (likely several hun-
dred CFMs). One thing to note is that I just wired the input to the
fan in parallel with the input to the PT so the more power that I 
push into the transformer, the faster that the fan will turn. Would
you all suggest running the fan on a seperate variac or just running 
it seperately all together and letting her rip at full speed at all times
the the coil is running? 

I am pleased so far with its performance, but I was wondering if 
some PFC caps would help to reduce the current draw a bit
and make sure that I stay within the power draw range of a 
standard 20 amp circuit on a 120 volt line? After all, that was the
main reason that I decided to construct this coil in the first place.
I have about (12) each of some 100 uFd, 370 VAC power factor
caps that I could cannibalize from another project that I no longer
have much interest in :^) I'm sure you would love to crunch the
numbers through your Java TC, Bart ;^)

I could post some pics if Hotstreamer still lets you post photos?
I have been concentrating so much on the large pig driven coils
in the last several years that I have just about lost my skills for 
building sub-pig sized coils <;^)

Thanks,
David

PS - the primary/secondary coupling is set so that the bottom
turnof the secondary coil is just about level with the top of the pri-
mary coil.
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