Re: [TCML] Secondary Damage (Large Coil)

[BrianB <brianb@xxxxxxxxxx>]

Amir,

I was formulating a response when I saw Brent's post which was exactly what I was thinking. 

On these bigger coils you need to be really careful not to over couple them or you will burn the secondary. The burnt turns you are getting might be the symptom of another problem. I'd measure your coupling and decrease it if necessary before trying out your repaired secondary.

Hope this is of some help,
Brian B.



On Apr 12, 2012, at 12:50 PM, bturner@xxxxxxxx wrote:

> Over-coupled??? Could be a spurious standing wave or something.
> 
> 
>> 
>> 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
>> 
>> 
>> 
>> 
>> 
>> 
>> 
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>> 
> 
> 
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