Racing spark problem
Mad_Micky, Tue Jul 31 2007, 12:57PMHey guys, I was just wondering if anyone could help me out with a problem I'm having with my new 8 inch Tesla Coil.
Performance is good at 3.5kVA but I get some quite nasty racing sparks near the bottom of the secondary winding. On closer inspection these sparks have caused cracks in the polyurethane coating. I just gave the coil another coat of varnish to repair the damage but I suspect this won't fix the problem. I read that these sparks can be caused by overcoupling or by an overly large topload. The coupling factor with the bottom turn of the secondary level with the primary is 0.147, according to JavaTC. I suspect my topload is too large, perhaps removing the sphere and retuning would help? Or should I try raising the secondary to reduce the coupling?
Attached are some photos of my setup and a text file of JavaTC outputs.
Thanks in advance for any advice.
]1185885154_879_FT0_tesla_simulation.txt[/file]
Re: Racing spark problem
Dago, Tue Jul 31 2007, 01:16PM
Raise the secondary and get a bigger toroid.
Dago, Tue Jul 31 2007, 01:16PM
Raise the secondary and get a bigger toroid.
Re: Racing spark problem
sparky, Tue Jul 31 2007, 05:17PM
Racing spark problem can be solved by raising the secondary for sure. I bet that is your problem. I remember ramming 4 kVA into my 4" TC system 2 years ago and I got plenty of racing sparks. Once I raised the secondary it changed the coupling coefficent and the racing sparks went away - I did also use a smaller topload and that changed the coils performance slightly. But I highly doubt that that your topload is too big - it looks just about right.
sparky, Tue Jul 31 2007, 05:17PM
Racing spark problem can be solved by raising the secondary for sure. I bet that is your problem. I remember ramming 4 kVA into my 4" TC system 2 years ago and I got plenty of racing sparks. Once I raised the secondary it changed the coupling coefficent and the racing sparks went away - I did also use a smaller topload and that changed the coils performance slightly. But I highly doubt that that your topload is too big - it looks just about right.
Re: Racing spark problem
Sulaiman, Tue Jul 31 2007, 08:39PM
I think it's more to do with close coupling to the bottom turns, not the overall coupling.
Raising the secondary will reduce both overall coupling and (in this case) more importantly, coupling to the bottom turns.
If possible a primary with a larger inside diameter may cure the problem and maintain good overall coupling.
P.S. I don't think your topload is too big.
Sulaiman, Tue Jul 31 2007, 08:39PM
I think it's more to do with close coupling to the bottom turns, not the overall coupling.
Raising the secondary will reduce both overall coupling and (in this case) more importantly, coupling to the bottom turns.
If possible a primary with a larger inside diameter may cure the problem and maintain good overall coupling.
P.S. I don't think your topload is too big.
Re: Racing spark problem
Hazmatt_(The Underdog), Wed Aug 01 2007, 12:42AM
Like Sulaman said, you're just overcoupled.
I was playing with a parabolic primary on my latest coil setup that had so much coupling on my 4" coil that it caused 5" racing arcs midway up the coil... which was kinda funny.
Try lowering your coupling to .1 and see how that goes.
Hazmatt_(The Underdog), Wed Aug 01 2007, 12:42AM
Like Sulaman said, you're just overcoupled.
I was playing with a parabolic primary on my latest coil setup that had so much coupling on my 4" coil that it caused 5" racing arcs midway up the coil... which was kinda funny.
Try lowering your coupling to .1 and see how that goes.
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