Once the magic smoke comes out, things don't work any more.

John Kasunich
jmkasunich@fastmail.fm
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Thu, 14 Dec 2006

Capacitor loses its magic smoke

Given the name of this blog, from time to time I will be posting pictures of components that have lost their magic smoke.

The current exhibit is a large (3" diameter x 8" long) electrolytic capacitor. I don't recall the exact value of the cap, it was between 3000uF and 6000uF, at 450volts. There were 12 of them connected in parallel as part of a large cap bank, and they were charged to 350-400V.

For some reason known only the the gods of electrolytic capacitors, this one developed an internal short circuit. All of the energy stored in the capacitor was immediately dumped into an arc deep inside the cap at the location of the short. In addition, all of the energy in the other 11 caps was also dumped into the arc. The total was several kilo-joules, discharged in a small fraction of a millisecond. Lots of energy deposited into a small volume very quickly means BANG!
(Click on pics for larger versions.)

(posted: 14 Dec 2006 22:08) (permalink)