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FU-811 (811A) VTTC secondary coil Problems

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Prof. TeraVolt

Wed Jul 06 2011, 07:21PM

Registered Member #3974 Joined: Mon Jun 27 2011, 06:50PM
Location: Germany
Posts: 23

I built a 811 VTTC a wihle back, and i am having problems with the secondary. the coil used to produce this kind of output:

now i added a new topload (stanles steel ball + brackout point) and the tesla coil is braking out at the wire that is leading to the new topload. and it wont brackout at the brackout point. :( i also tryd to wrap the wire in insulation tape (bad idea = Fire) but it dident work, well it did for a feu seconds but thain faild

and the topload in the video was a aluminum foil ball on a nail. :) works graite!!! but not with a steel ball :(

so what can i do to fix the problem?

oh and i forgot that the topload is sitting on a small insulator.

so what can i do about it?

Mads Barnkob

Wed Jul 06 2011, 07:59PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

If you read about steel and stainless steel here it could give you a possible explanation of your problem:

Prof. TeraVolt

Wed Jul 06 2011, 08:18PM

Registered Member #3974 Joined: Mon Jun 27 2011, 06:50PM
Location: Germany
Posts: 23

ok thanks, i will buy some aluminum spheres to replace the steel ones. i never thout that steel could have such a dramatic inpact on coil performance. :(
lol. is there any way to compensate for the steel either then buying new toploads?

Arcstarter

Thu Jul 07 2011, 04:40AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Well, try to solder the wire to your topload. That may help. Also, you do have a proper RF ground don't you?

Myke

Thu Jul 07 2011, 04:41AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

I don't think it has anything to do with the skin effect. Adding a topload would decrease the freq causing the skin depth to increase. I don't think the skin depth is really shallow at those freqs and there is a wide area. Even then, no significant current is flowing through the topload. I think it's not breaking out from where it should because of the E-field around the sphere. Try moving the breakout point farther from the sphere and try to smooth out the transition from the secondary to the topload as much you can so that it's less likely to break out there (due to a lowered E-field gradient).

Daniel Kramnik

Thu Jul 07 2011, 05:51AM

Registered Member #3885 Joined: Sun May 15 2011, 12:47AM
Location: Newton, Massachusetts, United States
Posts: 94

I had the same exact problem in the original version of my mini SSTC when I first built it - it broke out right at the end of the secondary coil instead of at the breakout point and burned through the secondary PVC pipe. The solution to the problem is to cut the PVC pipe so that it terminates around 1 - 2 cm above the end of the secondary windings and to make sure the wire from the top of the secondary makes good contact with the topload (some tape was enough in my case).In my SSTC, there were several inches of PVC in between the top of the secondary and the topload, I can see that the same is roughly true in your design.

Also, make sure that you aren't using too large of a topload on your VTTC. In my 811A VTTC, I found that a standard incandescent lightbulb wrapped in aluminum foil was the optimal size - anything else and the performance would decrease significantly or it would fail to break out altogether.

Finally, contrary to what Myke said, I have found that keeping the breakout point as close to the topload actually increases the performance of the coil. I use a thin lead from an electrical component bent into an L and taped to the top of the lightbulb as my breakout point.

Good Luck!

(btw, I'm Xellers on Instructables and Xkcdification on Youtube)

Myke

Thu Jul 07 2011, 08:12AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

Daniel Kramnik wrote ...

Finally, contrary to what Myke said, I have found that keeping the breakout point as close to the topload actually increases the performance of the coil. I use a thin lead from an electrical component bent into an L and taped to the top of the lightbulb as my breakout point.

Hmm. Yeah, you're probably right. Forgot that moving the topload downwards also keeps the top turns within the E-field.

Prof. TeraVolt

Thu Jul 07 2011, 03:23PM

Registered Member #3974 Joined: Mon Jun 27 2011, 06:50PM
Location: Germany
Posts: 23

lso add some turns on the conector to the topload. maby that would help? i alredy tryd to wrap the connecter in aluminum foil :D, dident have the efect i was looking for (it interupted the digital TV signel) (LOL) the main problem is that i cant co much about the coil former as im am bound by the crapy german stuf :(

and it workd for some time, untill i added the new topload, that is sitting on a 30 mm insulator.

it looks somewhat like this:

its the design for my AM VTTC. it has the same secondary dimenshons as the 811 coil. well the AM coils parts are much higher quality than my 811 coil but ok. so you can get an idea on how i mounted the topload

P.S. forgot the breakout point in the CG animation.

Daniel Kramnik

Thu Jul 07 2011, 03:50PM

Registered Member #3885 Joined: Sun May 15 2011, 12:47AM
Location: Newton, Massachusetts, United States
Posts: 94

Why can't you just grab a hacksaw or a dremel and cut the tube above the secondary windings? It makes a bit of a mess, but it's easy to clean the secondary off from PVC dust and if you do it right, it won't damage the windings. I do this all the time when I wind secondary coils. Also, winding the wire from the top of the secondary coil around the secondary former as you lead it up to the topload will definitely help, but not if there's too much space.

Prof. TeraVolt

Thu Jul 07 2011, 03:59PM

Registered Member #3974 Joined: Mon Jun 27 2011, 06:50PM
Location: Germany
Posts: 23

well if you have seen my animation you have seen that the topload is sitting on an insulator mounted onto a HT endcap that is in a HT connector that is siting on the secondary. + the ruber gasket that holds the connector is inposible to remove, only with considerable damage to the windings. and the space that the coils would be apart is abut 1/8" so not that far.

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