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Triggered SISG

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Terry Fritz

Thu Nov 09 2006, 11:12PM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi Finn,

It will "probably" be ok... TVSs are super fast and powerful, but the gate to source voltage really should not over shoot anyway. The 24V one in the SIDAC string commonly goes to about 30V with a significant current hit. but the Vgs TVS should just be "asleep" normally. The 100nF cap and 50 ohm resistor too it really control the voltage there.

Cheers,

Terry

Finn Hammer

Sat Nov 11 2006, 08:46PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Terry Fritz wrote ...

Hi Finn,

It will "probably" be ok...
Cheers,

Terry

I was lucky to find some 1500W TVSÃ¨s, so I have been building intensively today.

So far all 10 sections work well, when tested individually, but of course, the final proof lies in applying power.
I`l probably do that tomorrow.
I found a center point in the 250V SIDAC`s, which gave access to a 135V SIDAC, so this gap can be made to trigger from 1350V to 10000V

I give a couple of pics. to show today`s progress.
Here is the Fiber optic trigger transmitter, the receiver and driver board, and the SISG itself.

And here is the 10kV SISG itself in all it`s gory detail.

Big files, but what.....

Cheers, Finn Hammer

Terry Fritz

Sun Nov 12 2006, 01:07AM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi Finn,

So far all 10 sections work well, when tested individually, but of course, the final proof lies in applying power.
I`l probably do that tomorrow.

Beware that it will go from dead silent to a big arcing in 1uS!!! It still scares the crap out of me the way SISGs "suddenly" start up at full power!!!! You WILL understand soon

I found a center point in the 250V SIDAC`s, which gave access to a 135V SIDAC

Yeah, they are center tapped. See how I have brass shorting jumpers on the SIDACs:

They do seem to like being "evenly" distributed.

Very cool!!! No worries about not heat sinking the IGBTs yet. they run pretty cool even at 250 BPS!!

Cheers,

Terry

Steve Conner

Sun Nov 12 2006, 01:26AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

wrote ...
It still scares the crap out of me the way SISGs "suddenly" start up at full power!!!!

Finn just said that his new design could be triggered over a 1:10 range of DC bus voltages. So it can be started at low power and ramped up.

Terry Fritz

Sun Nov 12 2006, 02:37AM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Yes, of course!!!

In my case, the PIRANHA just sort of grew "UP"!! I never "reduced" the firing power

Even though the coil's "form" has changed very much, I still just fire it off "first time" at 4800V!! It always does just the same thing. But after major form changes, it is always "interesting"

But it has never done anything "bad".

Unlike a conventional coil on a variac, SISG coils are either "full off" or "full ON"!! Silent, or firing like crazy!! Once you get used to it, it is fine, but it is very different that we are used too... We'll see if Finn notices this crazyness in his work

) It is sort of hard to change the firing tap voltage, so why bother

I always warn "spectators" and myself before that it is going to go "SUDDENLY FULL ON!!", so prepare one's spine

The last spectator was Bob Golka (yes THAT "Bob Golka"

) He did not flinch

Cheers,

Terry

Finn Hammer

Sun Nov 12 2006, 05:55PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Today i finally had all 10 sections engaged at the same time. It functioned wonderfully!

The SISG gap, with these IGBT`s seem to favour operating conditions below 400Apeak, so to test the coil, I used 2 MOT`s in series, into a 50nF cap. At 150kHz, this gave me 400 Amps Pri Peak.

Notice that I am running the gap without any cooling finn`s, so I have to be real carefull to kep run times short not to overheat them.

I have a video here that shows the Triggered SISG gap in operation- Windows Media player will not play it, so right click and save!

What it shows is the coil, John Freau 4x13"toroid. The voltage applied to the primary is 4300 volts.
There is no breakout untill I press the trigger button, at which time it starts at 67BPS. First bang is then 0,46J, the following are 1,85J due to the charging choke.
I then crank the coil up to 1270BPS and back.
Starting power is 124W@67BPS, peak power is 2350W@1230BPS
Distance to the ground point is 30 inches, so I am not into spark length record breaking territory yet. But I guess that "Taming the SISG" is a feat in itself, so that can wait.
Scantesla! Is it able to figure out the best cap size @150kHz for maximum power and 400Primary amps max?
The help file says that the primary current limit is only for DRSSTC`s.

Cheers, Finn hammer

Terry Fritz

Sun Nov 12 2006, 09:09PM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Cool!!

You coil has a neat sound to it!! I think yours is the first SISG in Europe! - And the first triggered one!!!!

The help file says that the primary current limit is only for DRSSTC`s.

I "think" it will still work fine. Those functions are always turned on.

Scantesla! Is it able to figure out the best cap size @150kHz for maximum power and 400Primary amps max?

It should. You could also just graph peak current as a function cap size (mode 2). If you have any problems, send me the input file and I'll fix it.

Cheers,

Terry

Finn Hammer

Mon Nov 13 2006, 07:21AM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Terry Fritz wrote ...
You coil has a neat sound to it!!

Perhaps that is because the charging waveform still has a destinct 50Hz overlay on it. I
have not yet rigged up the 3 phase supply, because I have to go to the garage to do that, and it is cold there. (56 lat) So everything else better work well by then.

Anyway, someone asked for a schematic, here it is:

Pls notice, that when the SCR fires, the gap still is a SISG gap, only with a lower breaktown voltage. In my case, the section breakdown voltage at is 135Volts in the triggered state, and 1080Volts in the untriggered state.

Steve Conner

Mon Nov 13 2006, 01:24PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

This is great! I reckon our "toys" have more or less caught up with the commercial state of the art in pulsed power now.

Finn Hammer

Mon Nov 13 2006, 09:04PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Conserve Ten wrote ...

I reckon our "toys" have more or less caught up with the commercial state of the art in pulsed power now.

Thanks!
In that case I will have to change the source of current into the pulse line trough the gate transformers.
At present it is a humble 22ÂµF cap @16volts dumping current in 10ÂµS, producing a far from ideal (despite sufficient) waveform.
Now I will upgrade to a nice Rayleigh Line pulse forming network, where the inductance of the pulse line is also the output inductance.

Nice!

Cheers, Finn Hammer

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