by BillyBobJoe » Wed Nov 01, 2006 10:10 pm
<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by GalFisk
[br]For air, and gaps on the order of a millimeter, the breakdown is roughly a linear function of the gap length: V = 30pd + 1.35 kV, where d is in centimeters, and p is in atmospheres.
(<a href="http://home.earthlink.net/~jimlux/hv/paschen.htm">source</a>)
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I've been looking for this type of equation for a long time - Thanks!
But I'm confused as to what the V equals? Voltage in volts or kilovolts? Letts assume volts and I need to find how much of a gap at 7.48 atm (110 PSI) is needed for 7000 volts. So 7000=30(7.48)d+1.35 kv
d= 25.2cm
A 25 cm gap for 7,000 volts at 110 PSI? I don't think so - what am I doing wrong? I know this only works with gaps around 1 mm, but I should be getting a gap around 1 mm.
EDIT - Found this from the original site "Typically, the Townsend mechanism (and by extension Paschen's law) apply at pd products less than 1000 torr cm, or gaps around a centimeter at one atmosphere."
One atmosphere is about 760 torr, so this is pretty much useless? But still, it predicts a 1 cm gap for 1380 volts at one atmosphere. Definitely not right and it's still within the constraints of the equation. 'Effin math . . .