She caught fire today

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Re: She caught fire today

Postby Braditude » Thu Mar 05, 2015 12:36 pm

I've never had any flashover.
I wound my original primary as low as possible.
Also my primary was getting hot enough to melt the hot glue, so I re-wound the primary with Litz wire.
It changed the tune so I had to adjust the primary capacitor, but now runs cold. I also wound it as low as possible and raised the secondary with a couple of spacers. Seems to work good. Spark is about the same length as the original design. I need to fine tune the capacitor a little more.

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Re: She caught fire today

Postby bytecode77 » Thu Mar 05, 2015 12:41 pm

What's that tuning all about? I always hear about that, never tuned my coil and it sounds good. Can you explain that to me in terms a programmer understands?
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Re: She caught fire today

Postby Alex » Thu Mar 05, 2015 3:02 pm

the coil is made of two resonant circuits, one being the secondary and the toroid, and the other being the primary coil and the tank capacitor. The secondary and toroid have a resonant frequency, which must be matched by the primary circuit. Think of the resonant frequency of someone on a swing set. You (primary circuit) have to excite the swing at its specific resonant frequency to get the most efficient energy transfer. If you push the swing at the wrong times, the swing won't go very high, and you'll be quite tired (IGBT's won't be happy).
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Re: She caught fire today

Postby bytecode77 » Thu Mar 05, 2015 3:41 pm

So, how do I tune it? - I know there is a PDF that shows exactly how. But I'm a software developer and not an engineer, plus I don't have the appropriate equipment like an oscillator.
Also, the coil seems to run fine without tuning, is that just luck or are the differences in fact minor?
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Re: She caught fire today

Postby Alex » Fri Mar 06, 2015 8:58 am

you tune it by adjusting the number of primary turns.

If your coil is happily doing 20" then your coil is perfectly in tune. If it's less than 10" or so I would tune it. you don't need a ton of test equipment, you could just mess around with the primary coil until you get better performance.
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Re: She caught fire today

Postby SONYtec » Fri Mar 06, 2015 5:48 pm

pyrowolf wrote:I use a 60mm plexiglass tube to cover the whole secondary coil. It fits perfectly and i never have any flashovers. I made a flat 5-turn primary and have 20-22" sparks. Primary gets only slightly warm and igbts also stay pretty cool. I run the coil for up to one hour without issues. The plexi tube does a really cool job, and i even painted it black inside ;) .


Short video of the coil:

http://youtu.be/-0CZbzvHCTw

Cheers,

Wolf


Very nice!

Where did you get the tube to cover the secondary coil? And what length, thickness is it?

I want to do that with my kit with the original primary coil.
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