Re: Overcoupling?

To: tesla-at-pupman-dot-com
Subject: Re: Overcoupling?
From: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Sun, 09 May 1999 22:42:16 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

John Freau wrote:

> I've seen racing sparks occur just about anywhere along my secondary
> coils.  Often too-tight coupling causes racing sparks near the
> bottom of the secondary at around the height of the shallow inverted
> cone primary.  Other times, the racing sparks occur at 20 % from
> the bottom, 30 %, 50 %, 70 %, 90 %, or anywhere in between.  I've
> also noticed that sometimes, the sparks jump just a short distance
> of an inch or two, other times, the sparks seem to jump 4" or so.
> They may be traveling along the surface in a sense.  Sometimes the
> sparks loop out from the secondary, and look like the looping
> promenenses that loop out from the Sun's surface.

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