Alt-BEAM Archive
Message #02110
To: beam@corp.sgi.com
From: Steven Bolt sbolt@xs4all.nl
Date: Thu, 8 Apr 1999 12:30:42 +0200 (CEST)
Subject: [alt-beam] Re: capacitors exploding
On Thu, 8 Apr 1999, Paul B. Webster VK2BZC wrote:
> Benjamin Edward Hitchcock wrote:
>
> > So if you're working with capacitors at reasonable voltages (above say
> > 20 volts) please make sure that you get them the right way around.
> > They do explode.
>
> The voltage is irrelevant in this context. It's the *can*!
Meaning that the can has to be sturdy enough, or explosive force
won't build up. But the power creating the heat depends on amps and
volts.
> If you wire it in reverse, a large current can flow. This has
> relatively little to do with the capacitance or indeed voltage. The
> power delivery of your power supply is more important. It has nothing
> to do with discharge of the electrical energy,
Well... An electrolytic capacitor can be reverse charged, hold that
charge and even survive. But a prolonged reverse charge will cause
internal shorts, even at low voltages. Of course an explosive discharge
seems unlikely if no power supply is connected to help it along.
But things might be adding up here.
Anyway, let's respect significant stored energy and expensive
supercaps. Double check polarity, mind the voltage rating, play
safe. Regardless of the possible bang, the stuff inside those caps
(and TO3 power transistor cases, and so on) is not necessarily
harmless. You may let out more than just smoke...
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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