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Re: GE caps - the long answer ;-))
Original poster: "Jon Rosenstiel" <jonandcarol-at-adelphia-dot-net>
I've used the 42L's, (0.22 -at- 2000V) on my 5kVA pig powered coil. Had to run
30/string so they'd last a reasonable amount of time. At 20/string their
life expectancy was a minute or two. (Ends blown out) I bought them
surplus, (less than $1.00 each), so having to run 30/string wasn't such a
big deal.
I should also mention that when using Terry's original 0.056uF Panasonic
caps I had to run 15/string, ("normal" was 8 to 10/string), or they'd
overheat and rupture the case. I suspect the reason I had to run so many
caps/string is that my ballast, (Sears welder), was shoving a fairly large
"inductive kick" into the caps, well beyond what one would think. As the
saying goes..... "your mileage may vary"!
Jon Rosenstiel
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, November 09, 2003 2:07 PM
Subject: RE: GE caps - the long answer ;-))
> Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
>
> Hi Dan,
>
> I should have explained more...
>
> The 42L3332 caps are fairly high current snubber types caps. However,
they
> are full metalized film rather than foil / film. The metalization does
not
> attach well to the end cap material in such caps and high peak currents
> "may" blow them out. The super high current caps use actual metal foil in
> the plates to get very good attach and the end caps. The 42L3332 are
> pretty strong for a full metalized cap and they often do survive and many
> people have not had trouble with them. But, some people have had them
blow
> up too. It all depends on what the peak current in them is. So as a
> general rule, I would not recommend them. The full metal foil caps are
far
> stronger.
>
> Of course if one wants to use them or they are not going to super stress
> them, I can't stop them. But I just wanted to mention the warning:
>
> http://hot-streamer-dot-com/temp/GE42L3332.jpg
>
> The 42L3332 was actually considered a "good" cap for about a year until
> they started failing some people. I got a bunch of them sent to me and
> finally found the data sheet... Then we discovered the error. So many
> people said they worked fine... If one is going to use full metalized
> caps, these are probably your best bet. But just don't come yelling at
> Terry if they blow up. Enough people have already yelled at me for having
> them on the "good" list :-((
>
> The data sheet for the 42L3332 is at:
>
> http://hot-streamer-dot-com/TeslaCoils/MMCInfo/GE%2042L%20capacitor%20data.pdf
>
> Compared to the CD caps:
>
> http://hot-streamer-dot-com/TeslaCoils/MMCInfo/942C.pdf
>
> The dV/dT of the GE caps is 1000V/uS (remember you run them at 3000 volts
too!)
>
> The dV/dT of the CD caps is 2890V/uS.
>
> As an example, suppose we have a tank circuit running at 250kHz and we run
> the caps at full rated voltage. What is the peak current?
>
> GE42L3332: Gives 3000V/uSpeak
>
> CD9420C20P15K: Gives 2000V/uSpeak
>
> V = I x t / C or I = V x C / t so:
>
> GE = 990 amps peak
>
> CD = 300 amps peak
>
> Since the GE caps are higher value and higher voltage, they get hit with
> 3.3 times their peak current (330 amps)!!! In general, you can usually
get
> away with running them at 2X the rating for a short time in intermittent
> use. But officially, you should not run the GE caps over 1000V at
> 250kHz... I suspect Dan's string has fairly low voltage on the caps
> allowing them to survive?
>
> The CD caps are rated for 432 amps peak so they are "just fine!!" ;-))
One
> does have to derate a little for higher frequencies and all, but the CD
> caps just happen to fall in a nice "sweet spot" for value, voltage, RMS
> current, peak current, cost..... Thus is why we all recommend them so
much
> (always). There really is nothing that can go wrong with them unless you
> run them far over 2000 Vpeak, the frequency is super high, or the break
> rate is so high they overheat due to RMS current heating (a whole other
> animal!). Since LTR coils that run off NSTs are well defined, the given
> charts are very safe and the reports of failures are just about zero if
one
> also follows the "tips" too:
>
> http://thegeekgroup-dot-org/mmc/constrguide.html
>
> Forgive if we sometimes just "tell" people to get the CD caps. A ton of
> time, effort, experimentation, trial and error, failure analysis... has
> gone into all this stuff (6710 posts!! in the last two years, and I think
I
> wrote 1/3 of them ;-)))... So, we sometimes just hope people with "trust
> us" ;-))
>
> I am not sure the original poster understood there is a more to MMC caps
> than "polypropylene, voltage, and value". MMC caps are super high stress
> parts and we have to pick and choose them very very carefully!! They also
> have to take high frequency peak currents and substantial RMS currents
> too. It can get to be very messy trying to figure it all out. Thus, we
> just try to get people to use the well known and proven types of caps with
> nice design charts so all the work is done.
>
> http://hot-streamer-dot-com/temp/MMCcapSales.gif
>
>
> BTW -
>
> RMS current data is at:
>
> http://hot-streamer-dot-com/TeslaCoils/MMCInfo/MMCPower4.html
>
> CD9420C20P15K caps can be gotten from the Geek group:
>
> http://thegeekgroup-dot-org/mmc/
>
> Or from Richardson Electronics
>
> http://www.rell-dot-com/
>
> Lead times are usually 4 weeks from either. Rell sticks you good for
> shipping, but if you are going to get large quantities, you can save some
> money there. The Geek group has far better support, info, fast
> answers.... In normal quantities, they are the best source by far and
they
> are our pals too ;-)))
>
> Cheers,
>
> Terry
>
>
>
> At 08:23 AM 11/9/2003, you wrote:
>
> >I have to disagree with that assessment. I have been using these GE
> >type capacitors from the beginning
> >with zero problems running systems up to about 4kW on a single string of
> >these. The only time i ever smoked one
> >was while running when the coil is severely out of tune. I would
> >suspect other people have had the same thing. But, i've run these for
> >hours (intermittently of course - say one minute on time, five minutes
> >off) on end (for a few demonstrations i've done in the past year) with
> >no problems.
> >
> >Dan
> >
> > > Hi,
> > >
> > > I must mention that people have had trouble with these caps
> > > for MMC use!
> > >
> > > http://hot-streamer-dot-com/TeslaCoils/MMCInfo/good-bad.txt
> > >
> > > Cheers,
> > >
> > > Terry
> > >
> > > At 06:45 PM 11/8/2003, you wrote:
> > > >They are at Allied Electronics
> > > >
> > > >http://www.alliedelec-dot-com/
> > > >
> > > >Mfr.'s Part #: 42L3332
> > > >Allied Stock #: 591-6130
> > > >Manufacturer: GENERAL ELECTRIC CAPACITOR
> > > >Description: CAPACITORS, SNUBBER, METALLIZED POLYPROPYLENE, AXIAL, 5%
> > > >TOLERANCE, .33uF, 2000VDC
> > > >Current Page #: 999*
> > > >Previous Page #: 155*
> > > >
> > > >Qty. In Stk.: 305
> > > >
> > > >U / M:
> > > >1 Ea.
> > > >Min. Order Qty.: 1
> > > >
> > > >1-24 $4.800 Ea.
> > > >25-49 $4.360 Ea.
> > > >50-99 $4.000 Ea.
> > > >100-249 $3.700 Ea.
> > > >250+ $3.400 Ea.
> > > >
> > > >Terry Blake
> > > >http://www.tb3-dot-com/
> > > >
> > > >----- Original Message -----
> > > >From: "Tesla list" <tesla-at-pupman-dot-com>
> > > >To: <tesla-at-pupman-dot-com>
> > > >Sent: Saturday, November 08, 2003 6:38 PM
> > > >Subject: GE caps
> > > >
> > > >
> > > > > Original poster: Koen van den Berg <cerberus_rex-at-planet.nl>
> > > > >
> > > > > Hi there everybody,
> > > > > just another (short) cap related question: Does anybody
> > > know where I can
> > > > > buy GE 42L3332 capacitors (rated at 2kV DC .33uF)? One
> > > lead took me to
> > > > > Newark Electronics, but I can't find them there, or
> > > anywhere else...Any
> > > > > help would be much appreciated.
> > > > >
> > > > > TIA,
> > > > > Koen
> > > > >
> > > > >
> > >
> > >
> > >
>
>
>