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Re: Safety gap issues

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi JT,
Listen, there are many engineering practices dealing with high voltage breakdown. The figure of 30kV per cm is a well known figure that is a good ball park figure. We should all realize the "actual" breakdown will occur at different voltage levels under different conditions. The electrode shape, size, material, dielectric between electrodes, barometric pressure, temperature, etc.. all affect that figure. It is nearly impossible to be exact (which is why ballpark figures are there to at least, get you in the ballpark). To figure this out, just do what we do (research it). ;-)
William North of Los Alamos National Laboratory has a good write up which I think will help you understand some of the variables involved. You can download this particular chapter (7) at my website. 

http://www.classictesla.com/download/north7.pdf


Take care,
Bart

Tesla list wrote:


Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>

You said:
"The breakdown for air is approximately 30KV per cm. This is a local field strength and if the field is uniform (constant) then you can measure the distance to find the total breakdown. The 25KV per inch you found probably assumes a geometry and applies to a short range of distances. "
Well holy crap, that throws ALL my measurements with high voltage off a lot. My sparkgap for example is set at 7.5 to 8 mm. That means my sparkgap is set at 22.5kV? NO WAY; MY TRANSFORMER OUTPUTS 12KV ONLY. SO, IF IT WERE SET AT 22.5 KV, IT WOULDNT FIRE WORTH CRAP. 

THIS MEANS THE FORMULA:  1cm=30KV   cannot be correct

Thanks a ton for the help, but I THINK you're wrong buddy




From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: Safety gap issues
Date: Fri, 25 Nov 2005 08:00:02 -0700

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi JT,


Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>
Use a counterpoise? You mean putting large amounts of al foil, spread on the ground, as an RF ground? WTF no way dude, that ruins the aesthetics of my coil.
Counterpoise was for indoor operation. If you are outdoors and have a rod in the ground, GREAT. Keep the NST with the coil and ground the NST, secondary base, and strike rail to a common point and run a heavy short wire between this common point and the pipe in the ground (RF ground). Your target for sparks should be grounded to RF ground at the common point (not the pipe end). This keeps strike return current out of the heavy wire to the pipe and will help keep RF ground noise to a minimum. Ground your variac and line filter to mains ground.
The breakdown for air is approximately 30KV per cm. This is a local field strength and if the field is uniform (constant) then you can measure the distance to find the total breakdown. The 25KV per inch you found probably assumes a geometry and applies to a short range of distances. 

Gerry R.
i DO have a 4 foot Cu pipe driven into the ground, and 15 feet of wire is attatched to it.
msnip...