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Re: A triggered SISG coil



Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Finn,

Happy to see you are doing SISG stuff ;-))

At 02:45 PM 10/31/2006, you wrote:
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:

The charging time gets better at higher firing voltage and bigger primary caps.

http://drsstc.com/~piranha/PIRANHA/SISG-Timing-Calc.pdf

Yours looks fine. The main cap tend to overshoot to about 30V but quickly drops back down. The gate voltage hits a big flat spot as it turns on. The primary start up current looks fine. This program might be of interest:

http://drsstc.com/~sisg/files/SISG-Timing-Calc-100.zip

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"

I think you will like the SISG stuff!! Triggering has never been figured out before. Happy to see you are working on that too ;-)))

Cheers,

        Terry


Cheers, Finn Hammer