RE: Commercial caps / MMC

["sundog" <sundog-at-timeship-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi All,

 Didn't say you couldn't, and truthfully, I'd prefer to do just that for the
ability to choose my capacitance.  At the higher power levels, I can see a
problem with RMS current and the needed strings costing as much or more than
a commercial cap.  And the number of strings needed total for the current.
For a reasonably long runtime, 1 min on, 2-3 min off), I'd like the caps to
get warm to the touch, but not hot.  I'm also talking a 15kva+ setup, where
you're more likely to pop a breaker than anything.  The cost for the MMC
would grow fast at those power levels, and soon cost more than a commercial
cap.  I guess it'd be personal preference at that point.  I've noticed that
more pole-pig systems use commercial caps than MMC's.  And I've read in the
archives that commercial caps give better performance than MMC's.  I'm just
wonderin why.
									Caio
									Sundog


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, September 14, 2000 8:42 PM
To: tesla-at-pupman-dot-com
Subject: Re: Commercial caps / MMC


Original poster: "Robin Copini" <rcopini-at-merlin-dot-net.au>


Hi Sundog,

 Why can't you use mmc's with a pig? I have a 0.07 to 0.09 uF mmc,
(depending
on how many panels I use), that I run with my pig - (270V in = 40500V out,
or in
p - p terms, 57476V). Running for 5 to 6 minutes at a time with a 200bps
sync
rotary gives no discernible heating whatsoever, and monster arcs. It's like
everything else, you have to build the mmc to cope with the demands of your
proposed system. At a certain point, mmc cost will be >= commercial cap,
but then
what would you prefer if either cap dies, replace an mmc string, or an
entire
cap?

Best Regards,

 Robin in OZ.



Tesla list wrote:

> Original poster: "sundog" <sundog-at-timeship-dot-net>
>
>   Hi all,
>
>  Yup, more from the peanut gallery.  This time, it's *que dramatic music*
> Commercial cap vs MMC
>
>     Why do commercial caps reportedly give better performance than an MMC?
> Aren't they both an extended foil design?  Is it the inductance of the
> wiring in the MMC?  The caps themselves?  I made my strings, and last
night
> secured them in parallel to copper-clad PCBs, so I have a block of caps (7
> strings of 11 in a 4x5x12 or so block). DC test charge-discharge worked
> beautiful, and it looks nice too :)   Hopefully lowered the inductance a
> bit, and gave them a lot more conducting area.
>
>   I know that for small coils, MMC's rock.  They beat out commercial caps
by
> being "buildable", series/parallel them till you get what you want.  You
can
> add and remove capacitance in small amounts to test/tune, replace a failed
> string or individual cap, and not weep ower a blown commercial cap from
> overvoltage. You all *are* using saftey gaps, right? *right!?!*  :)  I
have
> to admit, I'd be a lot less scared of blowing an MMC than a commercial
cap.
>
>     What are the specs on the Hosfelt caps being used, and the price each?
> Maybe they can be ganged up on a pole-pig?
>
>
Caio!
>                                                                 Sundog