A triggered SISG coil

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Finn Hammer <f-h@xxxx>

All,

When I saw the SISG coil, I saw an IGBT stack 
with a safety gap across it. A basic building 
block that needed a trigger mechanism to really 
appeal to me. It should be triggerable even when 
using DC-Resonant charging, and it should be elegant. 8-)

I built a 2 section SISG because it would enable 
me to find out all the elemental things that I 
needed to know, and decided to start out with a transformer trigged SCR.
I selected the gate trigger toroid according to 
the TLAR criterium (That Looks About 
Right)  :-D  and so that the center would hold 
the insulation from RG214 antenna lead, because 
the toroids will be parked at elevated potentials.
The trigger wire is passed down the center of the 
toroids, and current from a 25µF cap is dumped 
down that wire controlled by an IGBT and a couple of triple5`s.

At the present moment, the circuitry looks like this:
http://home5.inet.tele.dk/f-hammer/boards.jpg

There are 4 250V sidacs in series, and the SCR 
bridges the bottom 3. Therefore I can trigger 
from 250Volts and up, and the top SIDAC will turn 
off the current in the string, in case the SCR should be unable to do so.
Suppose that I connect this gap to a resonant DC 
supply, which has from 250 to 499 volts on it. I 
can trigger it. After the ringdown the capacitor 
will be charged up to 998volts. The gap can hold it off untill I trigger it.
The way I wanted it.

It works great, although I am unable to get the 
fast charging times that you get, Terry:
http://home5.inet.tele.dk/f-hammer/250n.jpg
Yellow is main cap
cyan is pri. current
magenta is gate
Anyway, the final scope check without breakout:
http://home5.inet.tele.dk/f-hammer/ready.jpg

Before first light @ 988V off a single CD 150nF 942/2000 and about 3 inches
http://home5.inet.tele.dk/f-hammer/first.jpg
Nothing like a first light, particularly not when it is a real "first"

Cheers, Finn Hammer