Re: Ye good OL BRISG Tesla Coil
..., Sat Nov 18 2006, 10:33PM

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

Re: Ye good OL BRISG Tesla Coil
Terry Fritz, Sun Nov 19 2006, 03:48AM

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

Re: Ye good OL BRISG Tesla Coil
Daniel Uhrenholt, Sun Nov 19 2006, 10:50AM

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

Re: Ye good OL BRISG Tesla Coil
Finn Hammer, Sun Nov 19 2006, 03:45PM


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

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



Cheers, Finn Hammer

Re: Ye good OL BRISG Tesla Coil
Terry Fritz, Mon Nov 20 2006, 10:35PM

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

Re: Ye good OL BRISG Tesla Coil
Finn Hammer, Tue Nov 21 2006, 09:29PM

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.

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

Re: Ye good OL BRISG Tesla Coil
Steve Conner, Tue Nov 21 2006, 10:30PM

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!
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

Re: Ye good OL BRISG Tesla Coil
Finn Hammer, Wed Nov 22 2006, 09:32PM

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

Re: Ye good OL BRISG Tesla Coil
Terry Fritz, Thu Nov 23 2006, 01:50AM

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

Re: Ye good OL BRISG Tesla Coil
Finn Hammer, Thu Nov 23 2006, 06:34AM

The way I see it, you can look at the coil on a micro level, this would be the SIDAC/TVS /Cpri/Rgate/Rdischarge and IGBT loop.
Or on a Macro level, which would include the PSU, smoothing caps (if any) and the charging choke.

On the micro level, the SISG is stable, I cannot think of a way the tank cap can recharge before the IGBT stops conducting.
But on the macro level it is prone to oscillate, at least with a single phase supply, and a smoothing cap.
With a stiff 3phase rectified supply, I assume that the firing rate will be determined by the time at which the tank cap can recharge. It will modulate slightly around the rectifier frequency. In the case of a 6 pulse rectifier, 300Hz. 600Hz if someone went over the hill, and built a 12-pulse rectifier.
I`m sure this will be investigated in due course.

Cheers, Finn Hammer

Re: Ye good OL BRISG Tesla Coil
Steve Conner, Thu Nov 23 2006, 11:21AM

Hi Terry,

I didn't mean that there's anything wrong with the SISG. It works just like a static spark gap. What I mean is that DC resonant charging with a static gap, either regular or silicon based, is fundamentally unstable and not a good idea.

Re: Ye good OL BRISG Tesla Coil
Terry Fritz, Tue Nov 28 2006, 05:32AM

Hi Steve,

I didn't mean that there's anything wrong with the SISG.

Yeah, I know...

I "still" don't know how PIRANHA works so good for current limiting and "ballast"... Let alone the voltage multiplication... Darn "computer" figured it all out... They are smarter than "me" now I must think of a dual or even four MOT system based on PIRANHA... HARD to do since the "one" MOT system I have now will happily burn the house to the ground But two MOTs could at least run to the house's circuit "fuse" limit...

Cheers,

Terry

Re: Ye good OL BRISG Tesla Coil
Finn Hammer, Sun Dec 17 2006, 01:28PM

In another, more recent thread, Terry wrote:

So I thought it about time to try for the SISG spark length record. I wound a 3000 turn secondary for the OL-BRISG, and loaded it down to 42kHz. Today, at 4.5kiloamps Ipri. I got 60 Inches out of it.

Do I hold a record?
15.6µF @1050V, 300BPS takes 2.6kW, so it`s far from efficient.
Merry christmas to all from Denmark.

Cheers, Finn Hammer

Re: Ye good OL BRISG Tesla Coil
Terry Fritz, Sun Dec 17 2006, 03:59PM

Hi Finn,

Mark Dunn's coil and mine only do about 4 feet. Marks coil runs at 14400 volts but his primary caps are small since the main coil used to use a conventional spark gap.

So you do indeed have the world's record at 60 inches by almost a whole foot!!

Cheers,

Terry

Re: Ye good OL BRISG Tesla Coil
Steve Conner, Sun Dec 17 2006, 11:38PM

Congratulations and a merry Christmas to you too! It's interesting to see that your coil performs just as well as my OLTC2 did, even though the drive electronics are so much simpler and it only has a single brick. It used to give about 60" at 300bps too.

Of course, you can now do something I couldn't: increase the bang energy as much as you like by using a higher voltage tank capacitor and stacking bricks in series...

Re: Ye good OL BRISG Tesla Coil
Terry Fritz, Mon Dec 18 2006, 03:06AM

Yes indeed!!!

The PIRANHA-III should use 15 x 1000V IGBT sections. I went to four SIDACs like Finn since it is far easier to deal with 1kV increments instead of 900V increments %:-)

The "limit" I ran into was available power. 2400W 120VAC 20A circuits are pretty common here but not much more unless you get into the 220VAC stuff (hard for a "party coil" ). It all works out well for 700A peak IGBTs.

But if Finn can drive 6X the current with bricks!! 4500amps at say 15kV is one heck of a spark!! With the low loss of the primary circuit, you can use a "really big" primary capacitor without hurting the primary "Q" much... Hard to say right off for an estimate of how many joules per bang there. I am thinking "enough"

So the "limits" seem to be available power, how big of primary cap you can afford to make, and if the coil itself will just go up in a ball of fire I also note that with really big primary caps, open load peak to voltages get really high (Vo/Vi = k x SQRT(Cp/Cs)).

Merry Christmas to all!!!!

Cheers,

Terry