Re: Racing sparks Re: [TCML] Flashover Follow

[Miles Mauldin <teslamiles@xxxxxxx>]

Hi Jim,

So, increasing the top load, and making appropriate tuning adjustments has the 
potential to help with racing sparks?




________________________________
From: jimlux <jimlux@xxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Tue, December 7, 2010 10:48:30 AM
Subject: Racing sparks Re: [TCML] Flashover Follow

Gary Lau wrote:
> I think I disagree on a couple of points.  I don't think that bang *rate*
> affects the tendency to generate racing sparks, unless changing the rate
> also affects the bang *size*.  Its truly the bang size that matters.
> 
> In addition to the obvious method of raising the secondary to reduce
> coupling, I've also found it effective to raise the top load relative to the
> top of the secondary.  This may require the installation of a second,
> smaller toroid at the top of the secondary, to inhibit corona.
> 
> I think that increasing the top load size will also reduce the likelihood of
> generating racing sparks, as the top load voltage will be reduced with
> higher values of top load capacitance.  But one can't simply change the top
> load size without changing other things as well that will also impact racing
> sparks, so it's difficult to generalize.



The whole thing of racing sparks is a conundrum anyway.  Is it a "breakdown 
along the secondary" phenomena?  Reducing k reduces the voltage, so that attacks 
the problem at a sort of first principles level.  But, is it also a "uneveness 
of field" that aggravates it: larger toploads tend to create a more even field 
along the secondary, and so might "raising the secondary" or "removing inner 
turns of primary".. it might be that the k decrease is incidental, but what's 
really happening is that the field along the secondary is becoming more uniform.

Is there a fine scale (nanoseconds) timing issue?  As current flows into the 
topload, the voltage rises, but the rate at which it rises is determined by the 
resonant frequency, and also the relative size of the topload to the self C of 
the secondary itself.  Breakdown is known to be somewhat sensitive to rise time.

Is there a mechanism of charge distribution along the (insulated) surface of the 
secondary?  Has anyone ever made a "ridged" secondary (like HV insulators) to 
increase the creepage length vs air gap length?

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