Re: pure water capacitor?

To: tesla-at-pupman-dot-com
Subject: Re: pure water capacitor?
From: Terry Fritz <twftesla-at-uswest-dot-net>
Date: Wed, 16 Feb 2000 12:30:03 -0700
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme
In-Reply-To: <38AA446F.E84D5080-at-uwplatt.edu>

I know using water as a cap dielectric has been discussed in the past.
They say that the water would have to be ultra pure.  However, it would
quickly (like seconds) get filled with ions and contaminates once any power
was applied (or metal were just placed in it).  I also think it may be an
insulator at 1 volt but put 20kV across it and you may find it has an early
electrical breakdown.  Not the worlds greatest high voltage insulation
material ;-))  I think the "infinite breakdown" the book mentioned may have
had details...  

If water worked as a high voltage insulator, I can think of about a million
oil bath and ceramic insulation applications it could replace.  Since it is
used practically nowhere (SHIVA uses it I think???), I assume there is some
big problem.

Cheers,

	Terry

At 12:32 AM 02/16/2000 -0600, you wrote:
snip....

>I've been trying to do some research regarding design issues, when I came
>across a list of dielectrics for some materials for use in capacitors.  The
>dielectric constant for pure water is around 85 with an infinite breakdown
>voltage!  This means that two 12" x 12" plates spaced 1/8" apart will give
>a capacitance of .020uF!  I thought it would be a pretty sweet idea: a pure
>water cap in a plexiglass (or lexan (?)) box.  But, I have NEVER seen this
>mentioned anywhere I've looked.  The only problem I can see is
>contamination: everything has to be 110% clean before adding water.  This
>is do-able.
>
>Are there any reasons why I shouldn't try to use this?
>
>For the record, I'm looking at a 15kV/120mA+ NST.
>
>Thanks
>
>Mark
>