Re: MMC caps: prices, sources, and types

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

Original poster: DRIEBEN-at-midsouth.rr-dot-com 

Hi Michael,

I think someone said that an outfit called Richardson Electronis
has these same CD 942 polypropylene caps that the Geek Group sales
for about the same price if not even a little cheaper. I'm not too
sure what their webpage address is but I'm sure someone else on
this list does and if all else fails, I'm sure that a Google search
would locate them for you.

As far as how many MMCs to use, I'm not really qualified to comment
on that as most of my coils have used commercial pulse caps, but I
think that for amature purposes, you can construct your MMC so that
their total rated DC voltage about equals the output AC voltage of
your NST and they'll probably last darn-near forever. At least that
seems to be the concensus of the MMC users out there. If you were
going to use it for hours at a time for display purposes, then I
would probably go for the total DC voltage to equal at least 2X the
input voltage from your transformer for long term reliability.
The CD 942 series MMC caps are tuff customers and can stand up to
a lot of abuse and even have the self healing ability, which is good
for us amature coilers ;^))

David Rieben


----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
Date: Saturday, May 8, 2004 11:54 am
Subject: MMC caps: prices, sources, and types

 > Original poster: pepperman-at-softhome-dot-net
 >
 > I've been trying to price an MMC, but using the recommendations I've
 > generally seen (e.g. 3-4x the rated voltage of your transformer)
 > I've been
 > having a hard time finding a good source.  Putting that many in
 > series to
 > handle the voltage tends to mean you need more strings, which
 > significantly drives up the price.  I noticed that the Geek Group
 > tended to
 > not use as many in their MMC, and it seems to perform acceptably.
 >
 > So what would you say the minimum combined DC voltage rating (as a
 > percent of the transformer voltage) is to have an MMC that will
 > performacceptably and still have good reliability?  I'm not
 > overvolting the
 > transformers on a variac, so that shouldn't be an issue.
 >
 > I'm also looking for a good source for the caps.  I know the Geek
 > Group is
 > generally a very good source, but my time frame doesn't allow for the
 > delay it would take to get caps from them (they won't get another
 > shipment in until 5/31).  What other sources would you recommend for
 > good (and cheap!) caps?  And would any type other than the metallized
 > polypropylene caps still be acceptable?
 >
 > Finally, what would you say to expect to spend to put together an MMC
 > for a 1.5 kVA Tesla coil?  I'm not sure yet whether I'll be using
 > 10 kV or 15
 > kV transformers, so unfortunately I can't specify.  I guess if
 > 10kV, I'll be
 > trying to get 150mA, and if 15kV, I'll be trying for 90mA.
 >
 > Thanks for your help!
 > Michael Johnson
 >
 >
 >