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My newest coil

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williamn

Wed Aug 02 2006, 09:29PM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
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Posts: 149

I couldnt wait to finish this little DRSSTC so I rigged up a quicky to tide me over. I have been slowly building this little guy and finally have everything together. I reused the primary supports from my old mini coil but everything else includng the stand is new. The coil uses a HB of 30N60s and has a loaded Fres of 240khz. It should look pretty nice when I am finished wiring it up tomorrow. I have already flogged on it pretty hard and have not had any problems. The longest strike so far was 18", not bad for a coil that measures 15" total including the torroid. I have noticed that this thing really likes a high BPS and the ontime maxes out performance at about 60usec. I will eventually post it to the "Add your tesla here thread". I plan on bringing this one along my medium and big DRSSTCs to the Cheesehead thon. PS please excuse the poor picture quality I will take another tonight, if you look closely you can see the blue LED indictating the OCDC active due to the strike rail hit.

William

dan

Wed Aug 02 2006, 09:41PM

Registered Member #223 Joined: Mon Feb 20 2006, 06:42PM
Location: Ottawa, Ontario, Canada
Posts: 125

Nice little coil you got there! Especially with that spun aluminum topload.

I'm still using dryer ducting

Dr. Drone

Thu Aug 03 2006, 12:30AM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
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Posts: 1673

williamn

Thu Aug 03 2006, 01:27AM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
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Posts: 149

Hurray its finally dark enough to take some good pics! CR thanks the stand is made out of MDF, sealed then painted. I do not have the fans hooked up yet and the IGBTs get barley above ambiant after a few minutes so they don't seem to mind at all.

Update: One problem that I am having is when i run the coil without a breakout, I have not been able to coax out a streamer because the coil starts getting racing sparks when I start to turn up the on time from zero. My question is, is the coupling actually too high and the breakout just hides it? I do not get racing sparks or primary/secondary arcs with the breakout. Without I get to about 10usec ontime and all hell breaks loose.

Steve Ward

Thu Aug 03 2006, 11:50PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Hi Will,

Yes, the coupling is just too high to achieve breakout before achieving breakdown between the 2 coils. What size toroid is that? looks like 12"x2"? a 1" radius electrode should have a breakout voltage of around 140kV if i remember right. Of my coils, only my smallest DRSSTC can operate without a breakout point. The bottom turn of the secondary is about .4" above the top primary turn. My medium DRSSTC can run full input voltage and ON time, but does not achieve breakout on the ultra smooth 6"x24" spun toroid (breakdown voltage around 400kV i think), though the coupling is low enough that nothing "bad" happens... it just buzzes away.

So, you might want to try reducing your coupling. Java TC says my coils run around K=.17 or so. You will probably find an increase in primary current with lower coupling, but that is the trade-off to keep it from arcing. If your bridge design is sound, those IGBTs should be ok to about 500-600A at that frequency, so its not that big of a deal.

williamn

Fri Aug 04 2006, 01:50AM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

The torroid is a infounlimited 8x2. My coil is 8" x 3.5" wound with 32AWG with a calculated Fres of approx 240Khz(with topload). Thanks for the help Steve, I will slip on another ring to raise up the secondary a tad and report back, do you think I might gain a little more length by decreasing K?

Steve Ward

Fri Aug 04 2006, 04:11AM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

do you think I might gain a little more length by decreasing K?

Well, i did, but for a very simple reason. My spark length started to become limited by flashover between the coils, and the best way to insulate between them is more distance. So if you have flashover issues even with a breakout point, then you will need to lower the K to allow for longer sparks. Lowering the K generally increases tank circuit losses, so just keep that in mind.

williamn

Fri Aug 04 2006, 10:15PM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

Yep thats the ticket Steve, I bumped up the coil almost 3/4" on an inch before I stopped having racing arcs, now the first turn of the secondary is about .25" above the last turn of the primary, where before it was more like -.5". Now the streamers dance around like crazy, after the novelty wears off it kind of sucks because all the streamers do is strike the "strike ring"

williamn

Wed Aug 16 2006, 01:28AM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
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Posts: 149

Here is a new video of the coil running without a breakout. It runs great. The longest run time so far is 5 minutes straight and I only stopped becasue my wife was going to kick my ass.

Apparently she does not apreciate the song of a DRSSTC.

HV Enthusiast

Wed Aug 16 2006, 01:29AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Cool, very nice! Yeah, be careful of the wife . . .

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