[TCML] capacitors

[huil888]

(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 at SPP.ORG>
To: "Tesla Coil Mailing List" <tesla at pupman.com>
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 at pupman.com [mailto:tesla-bounces at pupman.com] On
Behalf Of Tom Trevethan
Sent: Monday, December 03, 2007 12:50 PM
To: tesla at pupman.com
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 at ff.vu.lt>:

> 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
>
>
> _______________________________________________
> Tesla mailing list
> Tesla at www.pupman.com
> http://www.pupman.com/mailman/listinfo/tesla
>

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