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Re: The manufacture of capacitors
At 05:25 PM 12/10/96 -0700, you wrote:
>> Subject: Re: The manufacture of capacitors
>
>>From gweaver-at-earthlink-dot-net Tue Dec 10 16:37:23 1996
>Date: Wed, 11 Dec 1996 06:22:47 -0800
>From: Gary Weaver <gweaver-at-earthlink-dot-net>
>To: tesla-at-pupman-dot-com
>Subject: Re: The manufacture of capacitors
>
>Tesla List wrote:
>>
>> >From ed-at-alumni.caltech.edu Tue Dec 10 13:55:53 1996
>> Date: Mon, 9 Dec 1996 18:05:21 -0800 (PST)
>> From: "Edward V. Phillips" <ed-at-alumni.caltech.edu>
>> To: tesla-at-pupman-dot-com
>> Subject: Re: The manufacture of capacitors
>>
>> Re: Oil dielectric capacitors
>> Why not go the whole way and eliminate the solid dielectric
>> material between the plates? I have an article in an old (circa
>> 1921) QST describing an 0.01 mfd, 30 kV capacitor using only oil
>> as the dielectric. Quite a construction job to get the plates
>> flat enough to avoid excessive average spacing, but genuinelyh
>> genuinely indestructable!!!!!! By the way, this one worked at
>> the "special" wavelength of 350 meters, or about 857 kHz, so the
>> inductance must have been pretty small.
>> Why doesn't some get ambitious? Or, more likely, will
>> someone who HAS been ambitious describe his results.
>> Ed Phillips
>
>
I once made an experimental cap like this. My results were less
than spectacular.
I first made one with 2 plates and then later 4 plates. I used plates
of brass sheeting. I used the brass as the aluminum flashing I had
wasn't heavy enough to stay in alignment and I had the brass on hand.
I used 5 nylons bolts. One in each corner and one in the middle. I used thin
nylon washers as spacers between plates.
I don't recollect the capacitance I measured as this was over 2 years ago.
The capacitance once in oil wasn't greatly different than the value in air.
The mineral oil I was using (from drugstore) must have had a rather low
dielectric constant. Certainly less than 2.
And the breakdown voltage was rather low even with the almost 100 mil spacing
between plate. If I remember correctly it was somewhat less than 5000 volts AC.
So considering the low capacitance and low breakdown voltage it was apparent
a workable cap of this design would be quite large.
8mils of poly inside the same plates gave nearly the same voltage
rating with much higher capacitance due to closer allowable spacing
between the plates.
The only advantages I could see doing this is total elimination of air
and the cap would be self healing in event of a breakdown. Perhaps it
would be better with a premium grade of oil or transformer oil.
my 2 cents.
Mike Hammer
mhammer-at-midwest-dot-net