BIG Capacitors

To: "'Tesla List'" <tesla-at-pupman-dot-com>
Subject: BIG Capacitors
From: Tesla List <tesla-at-stic-dot-net>
Date: Thu, 19 Feb 1998 00:18:38 -0600
Approved: tesla-at-stic-dot-net


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From:  Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent:  Wednesday, February 18, 1998 11:43 PM
To:  Tesla List
Subject:  Re: BIG Capacitors

Tesla List wrote:
> 
> ----------
> From:  Edward V. Phillips [SMTP:ed-at-alumni.caltech.edu]
> Sent:  Tuesday, February 17, 1998 11:54 AM
> To:  tesla-at-pupman-dot-com
> Subject:  Re:  BIG Capacitors
> 
> Justin:
> 
>         Any idea how big a 100 uF 18 kV capacitor would be?
> You can get 4800 ufd 450 volt electrolytic capacitors pretty
> cheaply at swap meets (less than a buck around here).  40 of
> those in series would be 120 ufd at 18 kV, if you could
> equalize the voltages with shunt resistors across each
> capacitor.  Since typical leakage is of the order of 2 ma,
> that wouldn't take too much power.  I have used one of these
> very successfully in a magnet charger, and think the series
> resistance isn't more than a couple of ohms.  Have looked at
> the can crusher page, but can't remember how many turns on
> the primary, so hard to judge what peak current is.  This
> may or may not be a foolish idea, but I'm sure discharging
> such a bank would be pretty spectacular.
> 
> Ed

Ed and all,

I suspect the big electrolytics couldn't withstand the voltage
reversals. This is not normally a problem with a magnetizer, since as
you know the coil is typically "crowbarred" (short-circuited) near the
first current maximum point, and the caps never see a reversal. However,
this is not the case for simple can crushers, where an 80-95% voltage
reversal is the norm... 

I think you're correct about it being a spectacular discharge especially
if the electrolytics explosively vented... :^)

-- Bert --