Re: Blown Capacitor!!

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

Original poster: "Alex Crow by way of Terry Fritz <twftesla-at-uswest-dot-net>" <user-at-alexcrow.clara-dot-net>

Hi -

To all taking part in this thread, I believe it's possibly a myth that MMC's 
are unsuitable for pig use. If you're using a bigger coil, several factors go 
against the intuition that an MMC isn't "big enough" -

- a larger coil will probably have a higher surge impedance in the primary 
circuit, certainly for frequencies off-resonance, reducing current.

- if you're going for LTR, you're going to have a bigger value cap, which 
equates to more strings, and the current will still be divided over those. As 
long as you don't exceed max dV/dT (and thus surge current), you'll be OK.

- resonant frequency will be lower, thus much reducing internal cap heating.

- you'll have to either buy bigger commercial caps anyway, or make a 
pseudo-MMC from them, and if you blow one - ouch!

There were a few comments on this subject sometime last year - try searching 
the archives.

Cheers,

Alex



On Wednesday 13 December 2000 12:06, Tesla list wrote:
> Original poster: "Robin Copini by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <rcopini-at-merlin-dot-net.au>
>
> Hi Ed,
>
>  I have a mmc that uses the 942C, (I got it right this time!!), series cap
> from CDET. My pig runs at 33Kv+/15Kva and I have yet to blow a cap. If you
> want to look, try my page below.
>
>  http://www.geocities-dot-com/rcopini/tcap.html
>
> The beauty of these caps is that if one blows, they are easily repaired and
> although the costs are consistent with a single commercial cap I know which
> one I
> would rather see 'let go'.
>
> Best Regards
>
>  Robin Copini.
>
> Tesla list wrote:
> > Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
> >
> > Hi Ed,
> >
> > At 04:01 PM 12/12/2000 -0500, you wrote:
> > snip...
> >
> > >Roderick,
> > >
> > >I know how you feel.  I originally built two rolled poly caps and
> > > destroyed both of them, along with a C.P. commercial cap.  It is a sad
> > > day.  Has
>
> anyone
>
> > >built a MMC cap for one of the larger coils running 5 to 15 kva? 
> > > Something in the order of .05 ufd to .10 ufd?  This might approach the
> > > cost of a commercial cap.  I now have in place a safety gap across the
> > > rotary to limit how much voltage the caps ever see.
> > >
> > >Ed Sonderman
> >
> > "My" original inspiration of getting into MMC work was Chip's infamous
> > "Halloween coil" explosions of 98 in which he fried two commercial caps
> > while running his big coil on the roof of his house (I wonder if there
> > are any pics of that??).  The giant bang noises and oil running down the
> > shingles is well documented in the archives of the time.  I remember
> > looking at the blown guts of the thing and thingking to myself "there are
> > better ways to make a cap"...  He has since made a big MMC out of
> > Panasonic caps and his coil has been running great ever since.  If Chip
> > has his ears on, maybe he could tell the number of rows and strings.  I
> > think it has like 350 caps in it but after blowing the $$$ commercial
> > caps, that was a bargain...
> >
> > Cheers,
> >
> >         Terry