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Re: 3MV/meter



Richard Hull wrote:

> All,
> 
> There was an old article By DC cox in a TCBA NEWS of yesteryear.  In this
> article he suggested single pulsing a Tesla coil to determine the actual
> voltage output.
> 
> He recommended DC charging of the normal tank capacitor and single firing
> the system.  The resultant non-ionic spark length would represent the
> actual output capabilities.
> 
> I have thought this out a bit and if you were to just align you gap for
> normal presntation with air flow or whatever quench method you use, and
> apply any DC voltage which will charge the cap to its air break over
> point in the gap, it will fire as a close analog to real operation.  Next
> a grounded object which is relatively flat should be moved in or out from
> the toroid (which has a moderately pointed object on it (the capacity
> will not assist in single shot storage).  Room lights should be out or
> very dim.  At the point where a true streamer arcs (not just a brush
> connect), this is the output of you coil based on the DC, 3 megavolt/
> meter, air breakdown rule.  It is important to closely mime the real
> conditions of your coil system to make this really hold.
> 
> A fan should be used after each shot to remove all ions prior to the next
> attempt.  Your tune may have to be moved back down the primary for best
> spark due to the absense of ion loading about the toroid.  Still, it is a
> better idea for the real voltage output of the coil than some arbitrary
> rule of thumb applied to running coils!  The result would be an informed
> estimate of a coil's capability.
> 
> There are problems with this method, but attention to detail and the
> realization that a lot of variables are still unresolved will put the
> test in proper perspective.
> 
> I'll try this soon with a small system first.
> 
> Richaard Hull, TCBOR


This is a very good test for demonstrating the 'single shot' capability of
a TC.  It is also proof that a coil does not bridge its full striking range
on the first shot, but instead must build up the arc from a relatively small
beginning.   

Regarding the breakdown voltage, it seems that the air will only hold off
roughly 800kV/m in this corner of the world using finite sized electrodes.
It's often useful to calibrate your test gap with a known high voltage rather
than rely solely on textbook values.

-GL

world using finite sized electrodes