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RE: Racing arc clues...

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Gary.Lau-at-compaq-dot-com>

Hi John:

I don't have the degree of experience that you have when it comes to
trying various top loads, but your theory about larger toroids promoting
racing sparks is not intuitive.  While a larger toroid's ROC may permit
a higher breakout voltage, it's comparably larger Ctop will also reduce
the maximum attainable voltage.  It's not clear which limit will

I've also seen racing sparks originating at the secondary base near a
sharp point on the primary.  High field stress points are clearly
involved.  Not coincidentally, moving the secondary away from the
primary reduces the stress as well as the coupling.  It couldn't be that
simple, could it?

And I've also seen racing sparks originating at some unremarkable but
consistent point anywhere on the secondary, presumably some defect that
generates a bit more corona than the rest of the surface, again
consistent with the high field stress theory.

Regards, Gary Lau

>Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
>Also, the addition of a too-large toroid will promote racing sparks,
>because the voltage builds up higher before breakout.  As the
>power is increased, a coil that did not have racing sparks before,
>may develop them due to the larger bang size.  The coupling has
>to be backed off at the higher power.
>Mistuning usually causes the racing sparks near the top.  Over-coupling
>can cause them mostly near the bottom, sometimes around the middle.
>But it can be chaotic at times, with racing sparks appearing almost
>anywhere.  Also, any sharp point on the primary, may promote racing
>sparks on the secondary at the area that faces the point on the
>primary.  In other words, areas of high field stress are more likely
>to develop racing sparks.  
>John Freau