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Re: SISG - PIRANHA Tesla coil first light!

Original poster: coolbluesky <coolbluesky@xxxxxxx>

Hi Terry,

Nice to see you are still refining the SISG design. I like your clever idea of using the brass bolts to adjust the Sidac firing voltage, why not set up a switch bank for the lazy... My question: what parts are you waiting on for your full-power test? The resistors? Do you still have the older SISG schematics on your site? I misplaced my copies, and would like to compare your latest schematic with the previous ones.

As a public service announcement for any new coilers to this list,
what would be the consequences of being hit by the streamer output of your fearful "PIRANHA" and its high currents. Would this design be ideal for first time builders?


On Aug 26, 2006, at 8:01 PM, Tesla list wrote:

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

I have been working on a powerful version of the SISG Tesla coil. I call it the "PIRANHA". Although it has had many forms, it is finally getting to a point nearing being "done", so I thought I would give an update...

It uses a single MOT and two of Mark Dunn's SISG boards. Firing voltage is somewhat adjustable by shorting sections of the SISG firing circuit with small brass bolts. I don't have all the parts to run at full power yet, but it can easily hit 28 inches at 67% voltage at low BPS. Break rate is "whatever it feels like" ;-) but about 60 to 360 BPS depending on the variac setting. Firing voltage is 2400V to 7200V in 300V increments.

Right now I don't have the right resistors and I really "should" make a new MMC for it, but every thing runs as planned. At full power it should near 45 inch arcs to ground. Some of the specs follow:

240 BPS
314kV peak output
33 Arms primary current(!)
650 Apeak primary current
2 x 8000V 330nF primary MMC caps in series
11 amps AC line current at 87% power factor.
Input voltage 100 - 110 VAC (keeps MOT out of saturation)

Actual power delivered to the streamer is about 450 watts. Earlier testing has shown the SISG coils like higher BPS at some advantage to arc length so this does all that easily. It's just about as much power as you can safely pull from a MOT without blowing everything up ;-) Primary RMS current is very high! At 33 amps RMS each IGBT will dissipate about 22 watts. Not a big deal with a fan breeze. The present MMC will burn up anyway ;-) So full power but "short" runs unless I want to spring $140 for a new super high RMS current MMC at twice the voltage. I'll burn this one up first :o))

The charging circuit is "new and improved" now. The old 1000 ohm resistor system would burn off 700W!!! But the solution was trivial to simply place the charge resistors so the SISG shorts them out during firing. Now they are 100 ohm resistors burning off just 50 watts of power ;-)) This also make a dual MOT system possible with very high RMS current parts! One could probably make a big pig system like this too. You don't really need a ballast anymore. The RMS current can easily be reduced as one wishes too. With higher voltage, you don't really need big primary currents, but there is no reason not to push it since the MOTs can supply more current than one can use ;-)) The schematic is here:


There is not much to it all all!! Just two simple resistors, two BIG microwave diodes, and a dual primary cap along with the SISG. Note that this system will NOT work with a standard spark gap! You get bonus points if you know "why" ;-))

Here are pictures of the "engine". Everything is bolted to an 11 x 14 inch piece of plywood:



All the files are here if you want to dig around:


But only these probably mean anything...