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Re: [TCML] capacitors
(un) Terry -
I think that "good/bad" list may be dated, and that the GE 42L-series caps
may have gotten a bit of an undeserved bad rap.
I know for a fact that several years ago people were building MMCs for
spark-gap coils using these caps, but under-designed the MMC rather severely
for both voltage and current handling capability, and were vocal when they
failed. I contacted several of these people off-line, and had them send me
samples of the failed caps for analysis. All showed evidence of either gross
over-voltage or over-current (melted end terminations and/or swiss-cheese
syndrome in the dielectric).
Back then, an on-line audio components company ended up with a large
inventory of various models of these caps, and were selling them very
cheaply in quantity (like $0.50 each for the .1uF 3KV part, and even less
for caps with lower capacitance and voltage ratings).
In the earlier days of MMC, Terry Fritz had performed testing of several
candidate MMC capacitors using a high power RF generator, and monitored
capacitor heating. The metallized-film GE parts did not have as much margin
as the film-foil Cornell Dubilier 942 series capacitors. However, I have
built several MMCs for spark-gap coils using these caps, and found the GE
parts to be reliable IF the MMC is designed to operate within the capacitor
ratings.
Since then, a number of people have used these capacitors in various types
of solid-state coils with complete success. Possibly those who take the time
to design, build and debug an SSTC pay more attention to matching the MMC to
the actual operating voltage and current requirements.
Regards,
Scott Hanson
----- Original Message -----
From: "Terry Oxandale" <Toxandale@xxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Monday, December 03, 2007 11:39 AM
Subject: RE: [TCML] capacitors
How can a correction be made to the polypropylene capacitor reference
list:
http://hot-streamer.com/TeslaCoils/MMCInfo/good-bad.txt
G.E. 42L4102 3000 0.01
The capacitance value is erroneous in that it should be .10 rather than
.01 uF. I found no "contact" information on Terry's site with which to
send an email on the error.
(un)Terry
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of Tom Trevethan
Sent: Monday, December 03, 2007 12:50 PM
To: tesla@xxxxxxxxxx
Subject: Re: [TCML] capacitors
Hi,
That's a big MMC - 200J per bang - IIRC about the same size as the one
used for
Electrum. What power are you planning to run at?
There is a useful list of good polypropylene capacitors for tesla coil
use here:
http://hot-streamer.com/TeslaCoils/MMCInfo/good-bad.txt
The Cornel Dubilier 942C20P15K (150nF, 2000V) seems to be very popular,
and I
have seen them advertised for $3-4 each. You would need 20 x 34 = 680
(approx
$2000).
Tom.
Quoting Tomas Stankevic <Tomas.Stankevic@xxxxxxxx>:
Hi,
what capacitors would you recommend me to build a 250nF @ 40kV MMC?
(for=20
DC TC powered by 3phase pig) how much (approximately) it will cost?
What=20
about shipping to Lithuania?
Toma=9A
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