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[moved] mini monster SSTC (plasma torch)

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LAN_403

Marko

Sat Feb 25 2006, 09:41PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

When I saw interesting royer-circuit schematic for 4,5mhz coil on this forum, and decided to try it (it didnt work at first, i swapped feedbacks and I had 4 ways to do it, lol)
I finally got it work, as stated on that topic, I used old SGTC secondary (not optimised too well)
When ran at 20 volts spark was qiet, 1,5cm long hazy plasma flame spraying out of breakout spike (it must be far from topload, otherwise e field doesnt allow him to break)

Spark is incredibly hot for coil's size, burns easily insulation, paper, steel wool,

Now I power it with 36 volth, half wave rectified and get 2,5 cm sparks as maximum (blew mosfet instantly at 40 volts filtered) , mosfets are IRFZ30 and IRFZ46 now.

This are old pictures, spark is now almost twice bigger (and camera smudges it, reducing its real size)

Also the film showing real power of tiny spark - burns insulated wire in flashes, smells awful (and blinds when looking at it)
Film is on rapidshare, go on ''free'' button and in 20 seconds you can start the download.
Crappy but only choice for large files (if you know some better sharing il be glad to hear)

In addition some bigger sparks, at 36V interrupted (cammera smudges spark a bit, it has tiny ends that are not visible reaching in air but they can be drawn)

So i opened this thread because i want to hear if anybody knows good way [list]to improve it, i wish to use more powerful mosfets (IRFP450) and 300V supply, problem is limiting gate V with zeners (coil didnt like 18V zener across)
This is the schematic (thanks to waverider)

Now with 36V supply it causes havoc in radio devices and tears down my ADSL connection, so I cannot run it for much.
Tried to cage it but she didnt like that (spark got smaller and coil started to fizzle, because it isnt (nor cage) grounded to reduce coupling to mains.

And forgot, I put a 4,7 nf cap across only half of primary (tried entire and two caps, but this worked best) and it improved stability, also made spark fatter.
Cap is not resonant at all, im wondering what it does in reality (tried 49nf, calculated to be resonant at 2mhz then lowered, i intended this to be primary resonant cap).

Cheers...

edit:
omg, i cant believe this, posted in high voltage...
Please can someone move this to TC, i would do myself but cannot delete topic, im really sorry...

...

Sat Feb 25 2006, 11:15PM

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

I think that using circuits like that are limited as far as spark length goes, just becuase of the inductive spike created blowing the fets (in my non-push pull self resonant like yours I blew 460's due to overvoltage at like 60v). You need to use a halfbridge or go class e...

As far as sharing the files; if they are <10mb you can put them into a .zip archive and upload them here.
Or you could use a site like putfile.com...

Marko

Sat Feb 25 2006, 11:33PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Actually gate blows readily because feedback overvolts them.
Mine are obivously >20 V, and live, i I put zener across they dont like it, it would be a must for higher voltage but i dont know would it work then at all.

PS.
Can please any moderator move this to TC forum

And atachments are 1mb only

flannelhead

Sat Apr 05 2008, 11:36AM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

I got interested in that circuit!
Marko, how exactly did you add the interrupter? And do you think that this circuit can run on 12V SLA if I make a 1+1 turn primary instead of 2+2? That should give 12V to the 1+1 turn feedback coil.

As I plan to operate this at kinda low power, say 10-30 Watts and the coil is really small (5cm x 6cm), should I be worried about illegal RFI interference? Should I make a faraday's cage?

Marko

Thu Apr 10 2008, 04:04PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Ah, remembering old threads, and how idiotic I was at that time, ignore my upper posts!

I wanted to post many replies lately but this week I'm pretty smited.

I don't see anything fruitful in a circuit like this. Push pull configuration without class E operation is a rather poor choice for driving an air cored transformar with high leakage inductance.

Without resonant capacitor of any kind the DC link inductor doesn't appear to make much sense, DS capacitance alone is way too small to properly resonate.

And in the end, the air-cored feedback coils introduce large phase shifts and are rather poor choice for feedback.
Just using a ferrite core would be a huge improvement, despite gate voltage problem would still remain.

If I for some reason really had to build a circuit with IRFZ44's and air-cored feedback coils I would probably arrange mosfets into a halfbridge.

There are still far more fruitful designs around for actually very little added cost.

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