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Re: Dielectric oil for a new capacitor (fwd)



---------- Forwarded message ----------
Date: Tue, 19 Jun 2007 12:00:04 -0700
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>, tesla@xxxxxxxxxx
Subject: Re: Dielectric oil for a new capacitor (fwd)

At 10:17 AM 6/19/2007, Tesla list wrote:

>---------- Forwarded message ----------
>Date: Tue, 19 Jun 2007 11:31:34 EDT
>From: ashumate3@xxxxxxx
>To: tesla@xxxxxxxxxx
>Subject: Re: Dielectric oil for a new capacitor (fwd)
>
>About mineral oil for horses. Do not use it. You have to remember you are
>using this with high voltage and what they sell for show horses does not go
>through quality and dielectric test.

The typical laxative USP white mineral oil (which is what you get at 
the feed store) might be reasonably dry and clean, depending on where 
and how it was packaged.  If they fill the gallon bottles themselves 
from the drum in the back....

However, if it's filled appropriately, it's not far off the real 
thing, and if it's cheap and available...

You can dry it with some dessicant or by carefully heating it to 
drive off the moisture.

Most amateur HV gear isn't well sealed enough to agonize about water 
content.  It's usually vented and exposed to the atmosphere, and so, 
will pick up moisture.  Yes, the breakdown voltage will be slightly 
less, but for most amateur applications, you're using the oil as a 
coolant and to displace air (i.e. running a NST sunk in a tank of 
oil) in which case even the crummiest oil has better insulating 
properties than the air it replaced.

If you're using it in something where moisture content and 
cleanliness is important (i.e. you're filling under a vacuum), then 
the USP oil is probably not what you want.  If you've invested the 
time and money in the gear for an application where the difference is 
important, you'll have no problem tracking down the insulating oil.

The big chemical difference (as opposed to water content) between 
things like Diala AX and USP White Mineral Oil is that the AX has an 
inhibitor in it to prevent spoilage.  The viscosity is also different 
which can be very important in cooling systems that depend on 
thermosyphoning over wide temperature ranges.  If you're filling that 
1 MVA transformer with the fins, you want the real deal.

Cost wise, they're both almost exactly the same price in large 
quantities.  It's the cost to put it into small containers and retail 
it that is different.


There's also more "geek cred" from having that bright yellow pail of 
Diala AX instead of a case of quart bottles of mineral oil from the drugstore.

>Ideally before you use oil it should be
>tested but many out there are not equipped to do this type of testing so the
>next best thing is to be sure of your source.
>
>Al Shumate
>
>
>
>************************************** See what's free at http://www.aol.com.