Re: oil for caps (fwd)

---------- Forwarded message ----------
Date: Wed, 14 Jan 1998 22:16:25 +1000
From: Ralph Down <rjdown-at-fan-dot-net.au>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: oil for caps 

Tesla List wrote:

> > Once again, I maintain that the selection of the type of oil will not
> > dramatically affect the capacitance value achieved.
> >
> > Ed Sonderman
> Ed & Ralph,
> I have to agree with Ed here. The air with a constant of 1 is being
> displaced by the SUNISO oil, and the increase is as we would expect
> with just mineral oil. To lay the thing to rest once and for all
> would be simple: perform the exact same experiment, but use mineral
> oil this time. If the results are about the same, then that would show
> that there is little or nothing to be gained by using oils of
> higher dielectric constant.
> HOWEVER, I believe that the looked-for increase probably WOULD show up
> if the cap was made using 6 mil poly!!! The reason here is that the
> thickness of the oil interface will now be much larger in proportion
> to the poly thickness. Note that this would imply TWO things at least:
> Higher dielectric constant oil COULD be used to increase the capacitance
> of caps made using THIN poly, AND such use of high dielectric constant
> oil WOULD put greater electric stress on the poly, because the
> proportion of thickness would be quite different with thin poly.
> Ralph, was your cap built using THIN poly? That would account for its
> increase.
> Hope this helps the discussion.
> Fr. Tom McGahee

Ed - I tried the same experiment using castor oil - with no appreciable
difference - .  I didn't realize the discussion was about various types
of oil having different effects. I used the Suniso oil mainly because of
its very high breakdown voltage. (I used to have the spec sheet - but
that was 2 years ago!)
Tom - The cap was constructed with approx 20 sheets of polystyrene 1/16"
thick and aluminium litho plates about 10" x 12".

Ralph Down