Re: Fair Radio 100KV Caps

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Scott Hanson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <huil888-at-surfside-dot-net>

Harold -
The manufacturer was Film Capacitors Incorporated, long gone. The Fair Radio
catalog claimed the "100 in series" setup; who knows what the actual
application really was. Every one that I have seen used just bare 1/4" - 20
steel studs for terminals. The case is polyethylene, and the nylon screw is
the fill plug for the dielectric fluid. The terminal construction indicates
that these are really not designed for high-current pulse discharge work,
but I don't remember anyone reporting having killed one in TC use.The
consensus is that the dielectric film is mylar, which is quite lossy at RF
frequencies. Just about everyone who has used them in a Tesla coil
application has mentioned that they get detectably warm after a few minutes
of continuous use. The next time I have my HP4284A LCR meter set up I can
measure the dielectric loss factor of the one I have. I made this
measurement several years ago on one of these caps but I don't remember
where I recorded the data. I seem to remember that it was very similar to
other capacitors I measured that were known to have mylar dielectric.

The dielectric loss data for a number of other commonly encountered types of
wound film capacitors is archived at
http://www.hot-streamer-dot-com/TeslaCoils/Misc/; the file name is "dissipation
factor test data 5-19-001.xls". This is an Excel spreadsheet showing
dissipation factor measurements at 50 kHz increments from 50 kHz to 400 kHz.
Sheet 2 is a graph that very clearly shows the two distinctly different
dissipation factors for mylar and polypropylene film caps. There is data
here on another model cap by FCI, a KM-9-65 rated .015 uF at 6500 volts.
This cap was unusual in that the dissipation factor was almost exactly half
way between the mylar and polypropylene groups, and the loss-vs-frequency
slope matched the polypropylene caps instead of the much steeper slope of
the mylar caps. Also interesting is the performance of a 'Custom" brand
(frequently marked "C-stom") wound cap using reconstituted mica paper
dielectric. This is the only cap tested that showed a decreasing loss factor
with increasing frequency.

Scott Hanson


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, November 08, 2002 6:53 PM
Subject: Fair Radio 100KV Caps


 > Original poster: "Harold Weiss by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<hweiss-at-new.rr-dot-com>
 >
 > Hello all,
 >
 > Back in (I believe) 1999, I bought some 100KV caps from Fair Radio
 > Sales.  These came out of an old government project which used 100 in
 > series.  Markings are F-C-I, KM14-1000-10, .01MFD-100KVDC, NOV
 > 1983.  Dimensions are 10X5X2.5" with two copper 1/4X1" threaded studs, one
 > on each end.  There is also a nylon screw in one end.  Case seems to be a
 > white PVC.  I used two of them in the coil I had at the Cheesehead
 > Teslathon.  They seem to work well for TC use, although one seems to be
 > getting a hot spot, when used with my static gaps, with the rotory, no
warming.
 >
 > Has anyone else gotten their hands on these, or have had a failure with
 > these? I cannot find the manufacturer for these and no one at any national
 > lab has either.  I would like to know what these are made of, without
 > trying to dismantle a working one.
 >
 > David E Weiss
 >
 >
 >