Re: MMC or Maxwell? Which is better?

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

Original poster: "S & J Young" <youngs-at-konnections-dot-net> 

Guys - let's call a truce.  A Maxwell capacitor IS AN MMC!  The only
difference is there are typically more caps in series and more strings in
parallel to achieve more reliability, and they are packaged in a nice metal
oil-filled box with nice HV feed-through insulators.  So we are talking
home-made vs commercially made MMCs.

It is a matter of economics and how much effort one is willing to expend to
make their own.  One can make MMC caps that are just as reliable as the
Maxwell MMCs.  If one has a source of cheap Maxwells that meet your needs,
than good for you - no reason to change.  For the rest of us, MMCs are ideal
because we can design them to be any capacitance and voltage rating we want.
We can do our own reliability vs cost tradeoff depending on our willingness
to gamble (run the caps at or beyond their ratings) versus make longer
strings with more strings in parallel and not worry about cap failures.  For
example I run 12 parallel strings of  12 .02 mF 2000V because I got a very
good deal on them, and I tend to be conservative in my designs.  But it did
take a lot of soldering!  Others are content with just one or two strings in
parallel.

--Steve Y.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, February 27, 2004 4:04 PM
Subject: Re: MMC or Maxwell? Which is better?


 > Original poster: "Christoph Bohr" <cb-at-luebke-lands.de>
 >
 > Hello Kreso, all
 >
 > Although I really feel sorry for your mishap I am somwhat happy to hear
 > this.
 > All scenarios where I was told that 37667 caps exploded under "normal" TC
 > use ended like this.
 > Of course if you stress a cap this way It is no wonder it will fail with
 > time.
 > Of course a concervative set safety gap is not a defense against all odds,
 > but I think if you had
 > ( been going on ) using this your cap might have lasted longer.
 > After a lot of pondering I will probably stay with my maxwell. If I wanted
 > the same capacitance and voltage rating
 > ( 60nF ( 2caps ) and 25 KV this would need a lot of CDE caps. I do not
doubt
 > this MMC would work great.
 > But I do doubt that I can sell the maxwells for a price that will pay the
 > MMC.
 > Nevertheless the Geek Group has done great work with theyr MM's. but as I
 > already have 3 of the 37667 caps already, two in use and one spare,
 > I will have to stick with these. OK, to be honest, somtimes I feel, I'd
 > rather have an equaly sized MMC ;-)
 >
 > This was or is the most euphoric thread I have seen on the list over the
 > last time, great fun to discuss with you all out there!
 >
 > Sincerely
 >
 > Christoph Bohr
 >
 >
 > ----- Original Message -----
 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Friday, February 27, 2004 3:25 PM
 > Subject: Re: MMC or Maxwell? Which is better?
 >
 >
 >  > Original poster: Kreso Bukvic <kreso.bukvic-at-kc.htnet.hr>
 >  >
 >  > I have 5 coils until now ( ops four i sold a small one on e-bay)! The
 >  > biggest project of mine was a TC with 10 kV 100 mA nst ( original
primary
 >  > voltage 220 V i used variac all the way to 260 so i guess there was
more
 >  > voltage out ). I like tesal coils i use them all day ( dont worry Terry
 > give
 >  > me a MMC and you will see it blew to the sky). This coil on resonant
rise
 >  > produced 4 foot sparks, i had a Gregs filter on the nst. One day i was
 >  > little bit on the mad side and wanted to see what this baybe can do and
i
 >  > stretched spark gap ( rq gap ) so wide it would barely fire wow it make
6
 > +
 >  > foot arcs so i leaved it that way! It worked for some time then i take
a
 >  > step up i remowed filter from nst ( resistors eat up some power ) and i
 >  > squezed a centimeter or two more of spark. Pity, safety spark started
 > firing
 >  > so i remowed it to and squezed a little bit more. Then the coil had a
 > 10-15
 >  > LONG runs in 2 days :-). Two days after i turned it on and BOOOOOM my
 >  > Maxwell well you allready know what happened! The i made SW caps and
 > result
 >  > was not so good so i used quick and dirty async gap that burned the nst
 > :-).
 >  > But im lucky my mate works at a local power platn and he just brings me
 >  > pigs, PTs and thast for free ( aint he good ). But i discard them
becausee
 > i
 >  > keep only the ones that have a nice voltage and that. Now i got a epoxy
 >  > potted nst rated for 10 kVac and want to make same sucess coil again. I
 > just
 >  > finished repaintin this PT, adding wheels , cables, ballastand and he
is
 >  > ready to rock&roll. But im experiencing a big problem there are no caps
in
 >  > Croatia so i must order internationaly. And i think using 3 - 4 kVac
cap
 > on
 >  > 10 kV power supply is BS by my calculation i would need 300 geek group
 > caps
 >  > ( 150 nF 2 kvdc ) and that is equal to 900 $ + shipping!!! I learned my
 >  > lesson about stretching the gap and so on but i seriously think and
know
 >  > that these caps if used by the chart will fail in a hurry. Il continue
to
 >  > thinks so until i see it with my own eyes and that is impossible ( you
are
 >  > all too distanced from me ).
 >  >
 >  > This is my web site click the 1000 W tesla coil! But first click ulaz (
 > sory
 >  > only Croatian ) :-)
 >  > http://free-kc.htnet.hr/Kreso-Bukvic/
 >  >
 >  > Best regards
 >  > Kreso Bukvic
 >  >
 >  > PS. Terry i would like to see the mmc that is overrated and works :-).
 > Nice
 >  > try.
 >  >
 >  >
 >  >
 >  >
 >
 >
 >