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Re: Tube coil capacitors



   The appeal of using many small units is flexibility when utilized with tube
coils. Some caps in the circuit only require 5 kV handling capacity (grid-leak
bypass, for example). Buy 100 of the right cap and you can probably supply
every
conceivable  value the coil requires. Plus, the Panasonic ECWH(V)'s use a
polypropylene dielectric. Highly desirable for coils.
   Actually, the capacitance/dollar ratio is vastly better with the larger
value
Panasonic caps. For example, in quantities of a hundred, the .001 uf sell
for .00178
uF/dollar, the .0056 for .00803 uF/dollar, and the .056 for .026 uF/dollar.
Paying
$215.00 for 100 .056 uF caps buys you 5.6 uF of capacitance. (1600 Vdc units)
   Still, there's no getting away from paying for good, new, commercial
capacitance.
And it seems there's a certain minimum physical capacitor volume that must
exist for
a given voltage and capacitance. You can't stuff .05 uF -at- 35 kV pulse into a
capacitor the size of a thimble.
    Interesting calculations Steve. Thanks for the input.
 Dave H.

Tesla List wrote:

> Original Poster: "Steve Young" <youngs-at-konnections-dot-com>
>
> These caps are probably fine (economical) for tube coilers operating at
> much lower voltages than typical disruptive TCs.  But they don't appear
> very economical for the latter.
>
> Based on Terry's experience, let's assume the caps can actually withstand
> twice their rated voltage.  So each cap is .0056 uF at 3200 VDC.  If we
> string 16 in series, we get .00035 uF at about 53 KV DC.  So a hundred of
> them would give us 6 times that or .0021 uF.  For most coils we would need
> an order of magnitude more capacitance, or about 1000 caps in
> series-parallel.  So the cost would be probably $600 per 1000, based on the
> $69.75 per hundred price in the posts below.  That's expensive, and a lot
> of soldering!
>
> Bottom line, probably more economical to buy a Maxwell or other commercial
> pulse cap.  Comments?
>
> --Steve
>
> ----------
> > From: Tesla List <tesla-at-pupman-dot-com>
> > To: tesla-at-pupman-dot-com
> > Subject: Re: Tube coil capacitors
> > Date: Thursday, February 18, 1999 5:18 PM
> >
> > Original Poster: Terry Fritz <twf-at-verinet-dot-com>
> >
> > Hi Dave,
> >
> >       The ECWH(V) series on page 324 of the Jan-Mar. catalog look
great.  They
> > were not available when I bought mine (pg. 322 P3521-ND  ECQP(U)).  The
> > things to watch for are dissipation factor and the word polypropylene.
> > These are both 0.1% at 1kHz.  The suggested applications of "high
> voltage,
> > high frequency, and high pulses" is another clue that they are made to
> > deliver high currents quickly with low loss.  Just the ticket for our
> > stuff.  These caps are probably better than the old micas.  One may have
> to
> > figure out which cap gives the needed value for the best price, but
> either
> > series should work very well.
> >
> >       Terry
> >
> >
> >
> > At 09:34 AM 2/18/99 -0500, you wrote:
> > >Terry,
> > >   Your testimony is encouraging. I really like the idea of combining
> many
> > small
> > >value caps to produce just about any value desired. Let's make sure
> we're
> > >talking about  the same thing. These caps are found in Digikey's online
> > catalog
> > >at http://info.digikey-dot-com/EC/V3/324.pdf (Don't have their current paper
> > >catalog) and are called "High voltage Metallized Polypropylene Film
> > >Capacitors"--ECWH(V). The 1600 Vdc, .0056 uF caps sell for $69.75 for a
> > hundred.
> > >
> > >   Are we on the same page?
> > >Dave
> > >
> > >Tesla List wrote:
> > >
> > >> Original Poster: Terry Fritz <twf-at-verinet-dot-com>
> > >>
> > >> At 05:10 PM 2/17/99 -0500, you wrote:
> > >> snip........
> > >>
> > >> >   I've considered one option: Digikey has Panasonic polypropylene
> caps
> > >> >rated at .0056 uf, 1600 vdc. They're fairly inexpensive, so multiple
> units
> > >> >could be purchased and series/parallel combined to produce just about
> any
> > >> >value  needed. The ability to vary capacitance is of obvious value.
> > Also, I
> > >> >wonder if the use of polyprop units will result in a higher  circuit
> Q
> > over
> > >> >that which would be effected by using Mica caps? snip....
> > >>
> > >> Other things have pulled me away from my many caps primary cap project
> but
> > >> I wanted to say that those Panasonic poly caps have performed with
> > >> excellence for me!  They run cold and have very high margin.   I think
> > >> mixing them together to get a desired value will provide a very good
> and
> > >> reliable device!  The 630 volt ones I use break at around 2400 volts.
> When
> > >> I take them apart (I am a failure analysis engineer), their internal
> > >> construction is very good.  I would not hesitate using them for any TC
> use.
> > >>
> > >>         Terry
> > >
> > >
> > >
> > >
> >