Re: [TCML] measure VDG voltage

[Jim Lux <jimlux@xxxxxxxxxxxxx>]

-----Original Message-----
>From: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
>Sent: Dec 23, 2007 4:13 PM
>To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
>Subject: Re: [TCML] measure VDG voltage
>
>Hi Jim,
>
>The ball gap used was 1.25" polished brass spheres (solid brass). The 
>gap arced at a gap distance of 0.35" (I started at .5" and closed the 
>distance in 0.1" increments). The gap arc voltage was 25 kV.
>
>I hear what your saying and your right that it will vary. I'm not 
>disputing that at all. The arc voltage will vary for many reasons. But 
>in a situation with a gap of normal TC size, likely between in the 26kV 
>range. My point is simple. Why use the upper end? Why not average the 
>value for better precision.
>
>I believe the arc voltage is based on electrode size and gap distance as 
>the major factors as long as the electrodes themselves are not jagged or 
>so small they are near point gaps. When you consider Tesla Coil sized 
>gaps, that's when I'm saying 26kV is a better number on average to use 
>(not the whole spectrum of gap sizes and gap distances). I'm thinking 
>mainly about Tesla Coil gaps and the gap sizes we use on average.
>

I fully agree... the 30kV/cm number is derived from the uniform field, and the gaps that most tesla coilers use are hardly uniform fiel (which is sort of the point I was trying to make.  your sphere gap was about 1/4 of the sphere diameter, which is typical of gaps that most TCers will be building.   Your number of 26kV/cm is probably a better number for practical use.  Most folks have fairly clean electrodes, so the debris, blasted off little pits, etc., aren't an issue.  Likewise, the small differences from material work function are probably negligible.




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