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Really big brick - Off-line SISG coil?

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J. Aaron Holmes

Fri Oct 13 2006, 03:28PM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

Test results (brief): It appears to work! No unwanted DC resistances, and the thing appears to turn on

Didn't get to play as much as I wanted, but it seems I do actually have the fixins for an OL-SISG

Still need to tinker a bit with the MMC figures, which is one reason why...

NeverStone C. wrote ...

Terry, I never quite understood your voltage doubler charging arrangement. As far as I can tell, it has to either fire at 60bps, or else only charge half of the tank cap for each bang. In the latter case it would waste 3/4 of the energy capability of the cap?

...this question interests me. In the more "classic" voltage doubler config with an SISG + primary across it, it seems intuitive that 60bps is what you'd end up with. Does this change in some subtle way with PIRANHA? You're talking about many 100's of bps. Of course 60bps isn't all bad; the caps will certainly be a lot happier!

Regards,
Aaron

Terry Fritz

Sat Oct 14 2006, 12:59AM

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

J. Aaron Holmes wrote:

Test results (brief): It appears to work! No unwanted DC resistances, and the thing appears to turn on

Cool! It should be good!!

Steve said:

Terry, I never quite understood your voltage doubler charging arrangement.

"I" never quite undersood how PIRANHA's charging works either

The "computer" figured it out while I was randomly trying different things. But the actual coil does work just like the MicroSim model, so it "does" work.

Here is what I know:

The MOT voltage can be fairly low (like 105VAC) to help keep the MOT out of saturation.

The primary cap is fairly "resonant" with the MOT which helps charge the two 330nF caps up to 1.5X the voltage. The primary cap value is not super critical and 200 to 400nF seems to work prety good too.

The system charges as a voltage doubler referenced to ground but discharges "floating". So the caps really don't discharge with respect to ground. Having the other cap discharge to a lower voltage helps the next cycle fire. It is almost "preserving" the firing voltage.

The BPS is pretty sensitive to the actual line voltage (variac). One can get from 60, 120, 240, "other" BPSs easily but it is touchy if you are trying to hit one exactly. Often the firing is fairly chaotic. ~240BPS seems like a nice area. The streamers "like" the higher BPS and the chaotoic nature of the thing.

Here is a Microsim model:

The firing rate at 106VAC input is ~220 BPS as shown here:

But look at those cap voltages!

The waveforms on the two caps are "messy" but they add up to the bottom waveform which is able to fire the 165nF combined capacitance at 220 BPS at 6900V!

Nothing really gets hot and the 100 ohm resistors just get a little warm. The system power is

220 x 1/2 165e-9 x 6900^2 = 864 watts.

The MicroSim model gives an RMS voltage of 106.066V and 9.668Arms:

So the VA is 1025.5. If we look at the real input power:

We get 911.6 watts. So the power factor is 88.9 Which is pretty good

The "loss" is 911.6 - 864 = 47.6 W The RMS current through the 100 ohm resistors is:

430mA so the power dissipation is 2 x 0.43^2 * 100 = 37 watts. That only leaves 10Watts on the IGBTs and primary ressitance! 0.25 ohms there seems "high"! It is proably a little lower! The IGBTs stay "cold" in the fan breeze.

So there, now you know just as much about it as I do

It is a bazaar thing and it works super good!! But the charging stuff is not "easy" to comprehend. I hope to figure it out "someday"

The PIRANHA is the only coil I use now and I have no desire to get out any of the others. Simple, light, never breaks, runs forever, and is a super good performer off a single happily running MOT. It is a scary coil in that it goes from dead silent to full power instantly, and it is loaded for bear!!

Obviosuly, it is the greatest Tesla coil design on Earth

I should probably advertize it more, but it will come in its time

It is a little tougher to get across since between the MOT and the coil, "nothing" is "conventional" at all... And I can still say that an SISG coil has "still" never blown up

Cheers,

Terry

J. Aaron Holmes

Sat Oct 14 2006, 02:18AM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

Terry Fritz wrote ...

And I can still say that an SISG coil has "still" never blown up

Heheh....well, that means the title of "First To Blow Up An SISG" will probably be mine

The more I look at the primary currents necessary to get any kind of coil power out of 600Vpk, the more scared I get!! Maybe I shouldn't just plunge in like this, but I'm so impatient!

I'm seriously considering going back and getting the other one of these bricks. There were two. $100 total (for two of these) seems pretty good if they work. Then I could scale up a bit with a MOT or something if things start to go well.

If I get a good bonus this year (and hide some from the wife), maybe I'll have to pick up one of those 6.5kV bricks to play with. Haven't seen any used ones yet, though, and I've been watching for a while...

Regards,
Aaron, N7OE

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