Re: Overcoupling?

To: tesla-at-pupman-dot-com
Subject: Re: Overcoupling?
From: FutureT-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Mon, 10 May 1999 16:49:06 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

In a message dated 99-05-10 06:30:02 EDT, you write:

<< The other discussion about static charges in the surface of the
> secondary gave me another idea: These racing sparks can be charges
> deposited in the surface of the secondary, moving due to the
> coil varying electric field. A varnished secondary coil can store
> significant charge at the surface, capturing charges from the
> ionized cloud that surround an operating coil.
> The small distance to the primary would result in charge spraying
> over the secondary coil by corona, enhancing the effect.
> The combination of a grounded conductive layer (the coil wire) and 
> a thin dielectric(the varnish) create a large grounded capacitance.
> These accumulated charges can create areas of relatively conductive
> material at the surface of the varnish, that serve as terminals and
> charge supply for the racing sparks. 
 >(A similar phenomenon is what makes MOS transistors conduct.
> Charges at the surface of a charged vertical capacitor move when 
> excited by a lateral electric field.)
> If this is true, coils that show racing sparks would also
> retain significant charges after turned off. The idea of gluing
> plastic rings spaced along the coil, or blocking corona from the
> primary with well rounded surfaces and added insulation could then
> be effective against "racing sparks". Another, more strange,
> idea would be to make the surface of the varnish slightly 
> conductive to impede the slow accumulation of static charges.
 
> Antonio Carlos M. de Queiroz
  >>

Antonio,

Some of my coils are coated with a single layer of water based,
Tripp Polyurethane, others are not coated at all, but all seem to
show the same kinds and degree of racing sparks, as far as I can
tell.  It can be a little hard to tell though, because the coils are of
different sizes.  In any case, none of my coating are thick; you can
still feel the ridges of the individual wires.  There's only enough coating
to just hold the wires in place.   

John Freau