Re: [TCML] Secondary Damage (Large Coil)

[Bert Hickman <bert.hickman@xxxxxxxxxx>]

Hi Amir,

The insulation between turns has been damaged, possibly by a strike to 
the winding, an arc-over from the primary to the lower part of the 
secondary, or by handling. Strikes to the secondary can be quite 
damaging on larger coils such as yours. At the very least you'll need to 
remove the windings around the affected areas, or remove the bottom 
portion of the winding since the coil form may now also be carbonized 
underneath.

Once the winding has been removed from the affected areas, scrape/sand 
away any traces of carbonization from the form before applying new wire. 
Once you have repaired the winding, you may also want to consider 
applying a thick 2-part polyester or epoxy coating over the winding. 
This will protect it mechanically as well as helping to prevent any 
future damage if you get another strike to the secondary. The strike 
will harmlessly spread out along the surface of the coating instead of 
destroying the insulation/wire at a single concentrated point.

Bert
--
Bert Hickman
Stoneridge Engineering
http://www.capturedlightning.com
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Amir Mojarradi wrote:
> Hello Everyone,
>
>
> My large secondary coil (12" diameter, 60" in winding length, 18 awg)
> has repeatedly exhibited overarcing at two specific points. A few
> months ago, I messaged the list, and decided to thickly re-varnish
> the damaged areas.
>
>
> Unfortunately, the problem has returned at the same two points. Since
> I am far away from the coil when I run it, I can not precisely
> determine the cause of the problem. From my research, I can infer two
> possible explanations.
>
>
> 1. Insulation (varnish and wire enamel) is exposed and/or damaged;
> there is arcing between two turns of the coil. 2. Insulation (varnish
> and wire enamel) is exposed and/or damaged; there is a premature
> breakout from a single turn of the coil.
>
>
> Below are pictures of the damage, to give a general idea.
>
>
> General Reference Image of the Secondary:
> http://www.flickr.com/photos/teslalightning/7068998821/in/photostream/
>
>
>
> Damage Point A:
> http://www.flickr.com/photos/teslalightning/7068998895/in/photostream/
>
>
>
> Damage Point B:
> http://www.flickr.com/photos/teslalightning/7068998945/in/photostream/
>
>
>
> Normal Coil Performance: http://www.youtube.com/watch?v=yjChcjVm5ks
>
>
> Any of these causes might necessitate a different solution. I am
> considering epoxying the damaged areas, using silver conductive epoxy
> to short out the arc, splicing the wires, or in the most extreme
> case, to re-wire the coil up to the damaged points and "surgically"
> soldering them.
>
>
> Would using a better insulating layer like Polyurethane or Epoxy
> help? What can I do besides re-wiring to solve this? Any related
> suggestions or comments will be extremely helpful, as any solution to
> this problem will require a meticulous undertaking.
>
>
>
>
> Thank you for your helpfulness and dedication to the hobby of
> coiling,
>
>
> Amir Mojarradi
>
>
>
>
>
>
>
> _______________________________________________ Tesla mailing list
> Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla



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