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Panasonic polypropylene caps (was Tube coil capacitors

>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! 

The cost of these caps appears to go down as the capacitance goes up.
While an array constructed out of .0056 uF caps would be expensive, the
cost is much less using larger value caps.  This line of Panasonic
polypropylene film caps, at 1600WVDC, goes all the way up to .056 uF.

I've run the numbers using the four largest cap sizes available.  Prices
are at the 100 piece qty.  I've assumed that a series-string of 16 is
adequate, and calculated how many string would be required to achieve a
.02 uf final value.  

Cap     Array   Final C         No. caps        Ea Cap          Final Cost
.033uF  16x10   .0206uF         160             $1.64           $263.20
.039uF  16x8    .0195uF         128             $1.77           $226.40
.047uF  16x7    .0206uF         112             $2.00           $224.60
.056uF  16x6    .0210uF          96             $2.15           $206.70

It's unclear if there is an advantage to using many, lower value strings
in parallel, to achieve a lower ESR value.

Terry, the search engine on the archives seems to be down, how many units
did you use in series?

<<<< I use 160 caps (0.1uF  630v) in four strings of 40 each.  They cost
$0.712 each/100.  A 20Nf cap would be about $280 but you need to mount and
connect them which adds about $50 if done up nice... If you by by the
thousand they go down to $0.42ea/1000 ... - Terry >>>> 

Regards, Gary Lau
Waltham, MA USA

> 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