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PIRANHA is here now :-D (New SISG design)

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Terry Fritz

Sun Aug 27 2006, 02:44AM

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

Hi All,

I have been working on a 'powerful' version of the SISG Tesla coil. I call it "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:

Typical:
240 BPS
6300Vfire
360kV 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)

If that is not enough, it can go to "eleven"

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

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 combined

) 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...

UPDATE:

I made of movie of PIRANHA running at low power but as much as I can till the new parts get here (2.7M):

Also hi-res pictures (~500k):

It is a DSL server, so if slow or clogged, try back a little later

Cheers,

Terry

ped

Sun Aug 27 2006, 12:35PM

Registered Member #305 Joined: Sat Mar 11 2006, 04:27PM
Location: Liverpool, UK
Posts: 29

What can i say, an amazing piece of kit, 1 question though,

i noticed youve mounted it on wood, and large wattage resistors appear to be screwed into the wood, is this right? or are they on insulating pillars? i had trouble doing something similar when the high voltage caused tracking across the wood.

Avalanche

Sun Aug 27 2006, 01:09PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

It's an unusual streamer you're getting with these coils, kind of has the consistency of an SSTC but with the crash and bang of a SGTC

I would expect it to be similar to what an OLTC would produce?

Amazing stuff anyway!

Terry Fritz

Sun Aug 27 2006, 08:59PM

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

Hi,

i noticed youve mounted it on wood, and large wattage resistors appear to be screwed into the wood, is this right? or are they on insulating pillars?

It's not "right"

But the aluminum standoffs are all I have at the moment. Ceramic standoffs are yet another thing I forgot to order

The plywood thing is a bit temporary just to work out the bugs. I have used wood a lot here in bone dry Colorado before, but these days I don't use it anymore due to leakage. The resistors are 500ohm not 100 (due in Tuesday) so they get 5X hotter right now, but they work for the moment.

It's an unusual streamer you're getting with these coils, kind of has the consistency of an SSTC but with the crash and bang of a SGTC

The SISG does not quench (yet) so the "on time" is probably longer than one would expect. The BPS rate is a bit random and tends to be high. DRSSTC, OLTC, etc. are at least "controllable". This baby is either off or going like mad

You just slowely turn up the variac, the fans start to spin up, and suddenly the thing turns on full blast and scares the crap out of me

Once the correct resistors are in it, the variac will probably not have a great effect on BPS at all. It would be good for a haunted house since it goes from dead silent off to full power in "literally" a microsecond(!) After a while, one does learn to mark the variac where it tuns on... It probably just needs a "switch" for a controller

I wish the movie was better. The Hi-8 to MPG conversion looses a lot... Even the sound is bad... but you get the idea...

It is a wildly fun thing!! No SISG switch has ever blown up

Not even Matrk Dunn could blow one up

But the present cap's RMS current and voltage rating are only 1/2 what they should be... I should shield it since it might be spectacular "when" I crank it up full

The IGBTs stay stone cold right now too which is a very good sign for going to far greater RMS current!

Oh! And just like clockwork, the &*$%*#%^ IGBTs are now on allocation

They were supposed to have thousands... but now backorders are out till late October... My Pal at Rel.com got me most of mine though

But in a way that is good since IR will make "many more" next time... They would be fine for DRSSTC stuff too since they pack higher current capability than any other TO-247.

Cheers,

Terry

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