Re: Another sad Aussie coil story, primary capacitance

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>

D.C. Cox wrote:

> Racing sparks simply means you have to low a value of capacitance
> on the primary and the coil is reaching highest potential at a
> point somewhere below the top of the secondary winding.

Perhaps some sort of 'forced resonance' :)

Gregory Peters wrote:

> Could I have some more detail on
> the primary capacitance causing racing arcs theory?

You'd need a chronic shortage of primary C to achieve this state 
of affairs, eg less than 1/4 the proper value.  Unlikely you're
so far out on the tuning!

This reminds me of another myth that is sometimes seen in Tesla
discussions - the idea that as you raise the base drive frequency
(CW) or primary tuning (traditional TC) the voltage peak at the top
of the coil migrates downwards.  It doesn't - in both cases the
voltage peak at the top stays put.  New peaks form at well defined
places within the coil which remain fixed in position and grow in
size as the primary frequency is raised (trad TC). With CW base
drive new peaks enter the coil at the base and migrate upwards as
the drive frequency is raised.

The following coil simulations illustrate the formation of a 
new voltage peak within the coil as the primary tuning is raised
from normal tuning (0%) up to 2.8 times Fres (+178%), all at k=0.2

0% tuning
http://www.abelian.demon.co.uk/tssp/pn040502/tfsm1-h1.anim.gif

+50% tuning
http://www.abelian.demon.co.uk/tssp/pn040502/tfsm1-ha.anim.gif

+100% tuning
http://www.abelian.demon.co.uk/tssp/pn040502/tfsm1-he.anim.gif

+178% tuning
http://www.abelian.demon.co.uk/tssp/pn040502/tfsm1-hf.anim.gif

In this example, a new voltage peak develops just below 40% height,
but a gross amount of tuning error is necessary to obtain it.
At the +178% tuning (for this particular coil), the primary
resonant frequency coincides with the secondaries 3/4 wave
overtone.

--
Paul Nicholson
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