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Ye good OL BRISG Tesla Coil

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Finn Hammer

Sat Nov 18 2006, 10:05PM

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

One great thing about being a seasoned member of this fine brotherhood of high voltage pulsed engineers is, that if the recipe starts with:
"You take an OLTC", well then I can go to the shed and drag out an old battered prototype.
And when the recipe continues:
"Then sprinkle with SISG topping", then I have recent experience with that too.
Ok, Enough hand waving.
The guts of the product, the Off Line BRIck siSG Tesla Coil, can be seen here:

To get the gate of the CM600 open, I used a 36V TVZ, a 200nF cap a 5Ohm Gate charging resistor and a 750ohm gate discharge resistor. The result can be seen here:

Resonant charging as usual,

Does it make sparks, oh yes! And this coil is one that appears to favour high break rates as seen on this short video, where I sweep from 63BPS to 1250BPS

Cheers, Finn Hammer

...

Sat Nov 18 2006, 10:33PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

fun stuff

Pretty good for an offline coil!

Although I beg you to get a new file hosting site, needing to type in a code, then wait 30 seconds, AND they only give you 20KB/s

Terry Fritz

Sun Nov 19 2006, 03:48AM

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

Hi Finn,

Wild!!!!!! Looks like about 30+ inches!!

I mirrored the movie at:

If one frame-by-frames the arc, there are some neat things going on there too!!

Looks like there might be some "cork screw" effects or something like tube coils...

Very cool!!!

Cheers,

Terry

Daniel Uhrenholt

Sun Nov 19 2006, 10:50AM

Registered Member #125 Joined: Fri Feb 10 2006, 01:52PM
Location: Aalborg, Denmark
Posts: 155

Nice work Finn!!!

I like the BRISG idea

You now know that the SISG work on some fairly big IGBT bricks, I wonder where this is going

Keep up the good work, it`s very cool.

Cheers, Daniel

Finn Hammer

Sun Nov 19 2006, 03:45PM

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

Terry Fritz wrote ...

Looks like there might be some "cork screw" effects or something like tube coils...

This might be explained by the near-CW operating condition:

tribledotting wrote ...

Pretty good for an offline coil!

Give me a break.
This coil is merely coasting along, as shown here, Ipeak=2.6kA

Cheers, Finn Hammer

Terry Fritz

Mon Nov 20 2006, 10:35PM

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

Hi,

This might be explained by the near-CW operating condition:

Wow! Yes indeed! 1200BPS is much higher than we are used to

This coil is merely coasting along, as shown here, Ipeak=2.6kA

Mark has had his SISG running with 14.4kV firing voltage (16 sections x 900v) and Finn has gotten to 2600 amps. That is over 37MVA!!! With Finn's trigger system now, the only thing the SISG has not done is quenching (we don't seem to miss it...). We may not have quite the control of a DRSSTC, but pretty close

I note Finn has not blown any IGBTs either unlike the DRSSTC systems tend to until they are all figured out

I am so happy that all this SISG stuff is working so well!!!

Weeeee!

As the saltwater cap is cheaper than MMCs, I suppose the "spark" gap will still be cheaper than SISG type systems... But "spark" gaps are sort of a "dead" technology now...

Cheers,

Terry

BTW - I also like FireFox 2.0's new inline form spell checking

It helps "me" a lot here

Finn Hammer

Tue Nov 21 2006, 09:29PM

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

Terry Fritz wrote ...

With Finn's trigger system now, the only thing the SISG has not done is quenching (we don't seem to miss it...).

I have a Stephen Conner Controller (TM), and it has full quench control. Based on the experience with it, I came to the conclusion, that there is no advantage in premature quenching (Quenching before the coil does by itself). We may think a coil performs better if it quenches at the first notch, and then jumps to the conclusion that if we force 1st. notch quenching then we get this good performance.
We don`t. The top load streamer complex is unable to process the power, that`s why it keeps ringing back and forth.
Some coils naturally quench early, (my old Ambassador was one) the power is effortlessly transferred to the streamer and I hope we can find out how to design coils that do so.
I guess the key word is impedance matching, and with the progress you have done in streamer modeling, I hope for a breakthrough in that line of design.

Terry Fritz wrote ...

I note Finn has not blown any IGBTs either unlike the DRSSTC systems tend to until they are all figured out

That`s right, the SISG crowbar feature does it`s trick!

And it is really funny to experience the change in coil behavior, when I turn the voltage up to a level where the trigger system is bypassed by the SISG voltage breakdown limit: The coil goes bananas

. The fuses get hot!

. The lights brown out

. The fuses blow

. The lab gets black. I got a kick!

Cheers, Finn Hammer

Steve Conner

Tue Nov 21 2006, 10:30PM

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

Hi Finn,

My experience with the OLTC controller was much the same as yours: When the coil is making sparks, the accurate control of quenching doesn't seem to matter much. So I think for practical purposes, Terry's new SISG thing, plus your SCR trigger circuit, is as good as my OLTC controllers ever were. Better even, since you don't have to worry about misquenching, and you can stack them to switch crazy voltages!

finn wrote ...
The coil goes bananas . The fuses get hot! . The lights brown out . The fuses blow

Does that mean I was right, when I said a SISG without triggering would be unstable with DC resonant charging? At least it protects itself from overvoltage with style

Finn Hammer

Wed Nov 22 2006, 09:32PM

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

Steve Conner wrote ...

Does that mean I was right, when I said a SISG without triggering would be unstable with DC resonant charging? At least it protects itself from overvoltage with style

I guess so.
The break rate increases to a point, where the power supply is unable to maintain the voltage, then there is a short break and it starts over again. Huuuiiiit, huuuiiit, huuuiiit

I tried this with a couple of the SIDAC`s shorted out, and the breakrate increased to 2564 bps @1200Apri

Cheers, Finn Hammer

Terry Fritz

Thu Nov 23 2006, 01:50AM

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

I am not sure I would call it "unstable". The SISG, or OL-BRISG, is still firing right on time exactly when it "should"

With the PIRANHA charging system, it is a bit "chaotic" but still doing just what it is supposed to do.

As long as it fires when ever the voltage reached the firing voltage it is fine. It is just a matter of how fast you can charge the system and how cool you can keep the IGBTs. In the case of those giant CM600's, they probably are not even warm yet

)

If you fire so fast that you get into the region before the SISG turns off, then I guess you would have a "power arc" type of situation where it really never turns off (but it might be able to "re-fire"). I guess one could consider a case where the thing is running in a pseudo CW mode too... But I don't see an obvious way that would work other than pushing the firing rate right into the ring down time. Like it would re-fire on every third cycle or something. But rates like that probably heat the silicon way up.

Cheers,

Terry

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