Re: Geek .15uF caps Was: "plate" capacitors

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Thanks Terry and David for clearing this up. I checked Cornel-Dublier for
specifications and requested one of their detailed catalogs, but so far,
haven't
been able to find detailed specs as I've seen with other cap manufacturers.
I did
download a pdf from them, but need to check it on the other pc. Terry, if
you do
get ahold of one of Chris's caps and test it I hope you'll find that magic C/w
number. The JavaMMC input is for lead "spacing" as designated and is
correct. It's
just that you need to know what that number is prior to input. Terry has a
list of
"known good caps" and I believe calls that data out for those caps. JavaMMC
also
calls out these known good caps info but not this particular data. This
will need
to be updated and explained in the program in further detail. The C/w has
always
been a bit confusing in all MMC programs which is why I'm trying to work "lead
spacing" as an input factor to calc C/w. I'm still not sure this is the best
method yet, but in time we will hopefully iron this magic number out
clearly. The
program will change accordingly.

Bart A.

Tesla list wrote:

> Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
>
> Hi,
>
> The "lead spacing" is sort of an odd number the capacitor manufacturers use
> as in indicator of the thermal heat/power dissipation for a capacitor.  The
> wider the spacing, the larger the cap, and the more heat it can dissipate
> without failing.
>
> Personally, I would go by RMS current vs. center temperature rise.  A
> hollow capacitor, sort of like a tube, should have much higher dissipation
> since the highly thermally insulated center is removed (hint, hint :-))
> The higher surface area outer windings are where all the capacitance is
> anyway (hint, hint , again :-))
>
> The length of the wire leads themselves is not a factor, but really how big
> and how much surface area the capacitor has to dissipate heat.  Testing has
> shown that the specified values are pretty conservative.  The Panasonics
> caps go to about 3.5 amps RMS at 350kHz before one needs to worry.  Even
> "i" pad the numbers some to prevent angry "customers" :-))  One really
> needs to put a thermal probe on the cap and run it with an RF generator for
> awhile in a still air environment to find the current needed to heat it
> about 10C and use that number as the current limit.  I have never seen the
> 942C series CD caps so I don't know this magic number.  I know the
> Panasonics well but Chris's caps offer a 2X cap/voltage advantage for the
> same dollar spent so the Panasonic's days are numbered ;-)  I hope to get
> hold of one of Chris's caps to test it, then we will now the C/W number for
> it...
>
> Personally, I think making these high power caps with the center hollow to
> dissipate significant heat from the center of the cap too would create a
> much higher current cap of the same value in the same volume.  However, I
> don't want to give out too many hints :-)))
>
> Cheers,
>
>         Terry
>
> At 06:03 PM 4/19/2001 -0700, you wrote:
> >Hi DK,
> >
> >Good point. I haven't built an MMC before, so I could be off there (lead
> >length vs. lead spacing).
> >Terry, can you fill us in on lead spacing?
> >
> >Thanks,
> >Bart A.
> >
> >Tesla list wrote:
> >
> >> Original poster: "David Knaack by way of Terry Fritz
> ><twftesla-at-uswest-dot-net>" <dknaack-at-rdtech-dot-com>
> >>
> >> > Original poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net>
> >> > The JavaMMC Designer should help you check this out for yourself.
JavaMMC
> >> > uses the caps lead length as an input.
> >>
> >> Unless I misunderstand, I think thats the horizontal spacing,
> >> not the lead length.
> >>
> >> In that application, what does the item referring to the 'primary
> >> resistance' mean?  Resistance of the coil primary?  That should
> >> be very, very low, correct?
> >>
> >> Also, do you happen to have a ballpark figure for the capacitance
> >> of the Geek Group bucket capacitor?
> >>
> >> thanks
> >> DK
> >