Re: oil for caps (fwd)

---------- Forwarded message ----------
Date: Mon, 12 Jan 1998 16:58:51 -0500
From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Cc: Esondrmn-at-aol-dot-com
Subject: Re: oil for caps (fwd)

> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: oil for caps (fwd)
> Date: Monday, January 12, 1998 1:48 PM
> ---------- Forwarded message ----------
> Date: Mon, 12 Jan 1998 13:27:33 EST
> From: Esondrmn <Esondrmn-at-aol-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: oil for caps (fwd)
> In a message dated 98-01-09 02:01:20 EST, you write:
>    -  snip  -
> << 
>  Fellow Coilers.
>  I made the original post re SUNISO oil and its apparent effect of
>  increasing the expected capacitance of a stacked plate cap (aluminium
>  litho plates and polystyrene dielectric).
>  I was concerned that possibly my findings were in error, so I set up a
>  small test as follows:-
>  I built a very rudimentary cap consisting of 4 aluminium litho plates 
>  7" x 5" separated with 3 sheets of polystyrene 1/16" thick.
>  The unit was taped together and the capacitance measured with a
>  Parameters 7060 multimeter as .000635 uF.
>  I then lowered the unit still connected to the multimeter into a
>  container full of Suniso 3GS refrigeration oil.
>  The capacitance steadily rose as the capillary action sucked the oil
>  between the plates to .000747uF. But stopped there due to air trapped in
>  the centre of each plate.
>  I dismantled the stacked plate and reassembled wet (painted each plate
>  with oil) and the measured capacitance was .000859uF.
>  This was only a quick and dirty experiment which you can all duplicate
>  with virtually no expense.  The results show quite clearly that the
>  Suniso 3GS oil does in fact increase the expected capacitance.  This
>  particular test did not show an increase of 100%, but never the less
>  there is an increase.
>  My original cap ((.02uF) - which should have been .01uF using the TESLAC
>  program) is still functioning and hasn't missed a beat in 2 years! is
>  used with 4 x 10kv 30mA neon trannies in parallel driving a 9" x 25"
>  secondary, with a 1/4" copper flat spiral primary - 9 turns tapped at
>  7.5 - produces 4 foot streamers consistently using a single spark gap
>  (brass coach bolts - about 1/4" gap).
>  Regards
>  Ralph Down
>  Keyboard Electronics
>  Gold Coast
>  Australia
>   >>
> Ralph,
> I thought the original question here was whether or not one type of oil will
> yield a higher capacitance value (significantly higher, like double) when
> compared to say mineral oil.  Your test shows that a cap with polystrene and
> oil produces more capacitance than a cap with polystrene and air.  No
> here, I would expect that.  I calculate that your test cap should produce
> about 978 pf - and you measure a little less, which is also expected as the
> caps we normally build end up with a spacing between plates a little more
> the measured thickness of the dielectric due to everything not being
> flat and insuffecient pressure holding the plates together.
> 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

Hope this helps the discussion.
Fr. Tom McGahee