Re: [TCML] coin shrinking

[David Sharpe <sparktron01@xxxxxxxxx>]

Mark
You'll definitely need hockey puck diodes at at least 2X DC pk on
capacitors.  The severe reverse recovery currents (dI/dt) may blow them
out as well.  I'm using 16 (2 parallel x 8 series 450WVDC electrolytics
650uF total at 3kVDC, right at 3kJ.  Models at 25kA, estimated
peak of around 18kA.  No blow ups (yet KOW).

Got about 100 of them out of demo'd multi-megawatt UPS's for
nothing, "get em or dump em".


On Sun, Oct 27, 2013 at 10:13 AM, Mark X2 <susax2@xxxxxxxxx> wrote:

> I was thinking of getting some hockey puck diodes, if I can find them, to
> cope with the reversal voltage.
> Maybe putting some caps in series for a higher voltage would be a good idea
> to prevent the contacts of a high voltage switch from welding together.
>
>
> 2013/10/27 David <drieben@xxxxxxx>
>
> > I believe the Geek Group built a quarter shrinker comprised of multiple
> > large electrolytic capacitors that worked. It's my understanding that the
> > dV/dT is much better for this though, with the higher voltage pulse caps
> > (say like 10's of kV at 10's or 100's of uFds.) And as you've stated, the
> > voltage reversals can be problematic for electrolytics. But since you
> > already have them....
> >
> > David Rieben
> >
> >
> >
> >
> > Sent from my iPhone
> >
> > > On Oct 27, 2013, at 6:26 AM, Mark X2 <susax2@xxxxxxxxx> wrote:
> > >
> > > Hi guys,
> > >
> > > recently I've purchased 50 6800uF 350V electrolytic capacitors and I
> was
> > > wondering if I could use these in a capacitor bank to shink coins. I
> know
> > > the reverse voltage may pose a problem, but I know there are ways
> around
> > > this. Tips or ideas are very welcome.
> > > Regards,
> > > Mark
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-- 
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA USA

Sharpe's Axiom of Murphy's Law
"Physics trumps opinion!"
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