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Distance problem with 120 Kvolts DC

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Forrest S. Campbell

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May 26, 1996, 3:00:00 AM5/26/96
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Hello:
I am new to these voltages and I'm trying to find the best way to
reduce the free air distance to ground from 12 inches lab air to 6
inches.
I am going to use a 1/2 " thick plexiglass(lucite) between the high
voltage source and ground. Then reduce the distance from the high
voltage DC source to ground by 6 inches. I've been told that a charge
might build up on the plexiglass "shield" and cause some local arcing.
a)Is this the best way to go??
b)Is plexiglass the right choice ??
Any help would be appreciated.
Thanks:
Rabbit11

BOB ROGERS

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May 27, 1996, 3:00:00 AM5/27/96
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In article <4o8dds$4...@dfw-ixnews10.ix.netcom.com>, rabb...@ix.netcom.com(Forrest S. Campbell) writes...

The generally accepted value for breakdown in air is 30 kV/cm or 75 kV/in.
So a 6" gap should withstand about 450 kV without any plexiglas. It is
the gradient you must control so you need to make the high voltage electrode
nice and round - I would guess 1" to 2" diameter would be enough for the
voltage you are trying to hold. It's true that both the absolute voltage
and the gradient are involved in the breakdown phenomena but getting the
gradient under control is the first step.

Bob
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