3
\$\begingroup\$

For my studio photography I have a set of Prolinca strobes rated at 500 Ws. They fire in 1/2000 of a second, meaning that they deliver \$\frac{500 J}{1/2000 s}=1MW\$ for a jiffy. (No wonder that this causes a rather loud "clac" sound.)
I've always wondered how the capacitors can survive this. Are there electrolytic capacitors which allow repeated shorting?

(If the caps work at rectified 230V they must be 10 000\$\mu\$F to store 500J)

\$\endgroup\$
4
  • 1
    \$\begingroup\$ Is a jiffy a scientific term? \$\endgroup\$
    – Majenko
    Jun 17, 2011 at 17:48
  • 1
    \$\begingroup\$ @Matt: Yes. en.wikipedia.org/wiki/… \$\endgroup\$
    – endolith
    Jun 17, 2011 at 18:31
  • \$\begingroup\$ So which definition are we working to here? Isn't it about time SI got hold of it and standardized it? \$\endgroup\$
    – Majenko
    Jun 17, 2011 at 18:34
  • 2
    \$\begingroup\$ 1/2000 seconds isn't that fast, only a few hundred millijiffies at most. \$\endgroup\$
    – Olin Lathrop
    Jun 17, 2011 at 21:33

1 Answer 1

Reset to default
6
\$\begingroup\$

There are capacitors designed for flash-bulbs, they can withstand higher currents but still probably not shorts.

These lamps are not shorts, for 1/2000s peak current must be somewhere at 4000A, which means for 230V resistance should be 47mOhm, so good caps in parallel might have lower resistance, and dissipate most of power in wires, connections and lamp itself.

You may add inductor in series with your lamp to limit peak current.

I am working on similar problem - I've got 2x 2000J flash-lamps (used in Russian aircrafts), and already bought a bag of capacitors for them - going to try it soon :-)

\$\endgroup\$
5
  • 2
    \$\begingroup\$ Good advice: don't stare into them when you fire them. You don't see anything anymore for half a minute :-). Success! \$\endgroup\$
    – stevenvh
    Jun 17, 2011 at 18:02
  • 1
    \$\begingroup\$ Yeah, I've flashed 150J lamp accidentally in my hands... This lesson is very very hard to forget :-) \$\endgroup\$
    – BarsMonster
    Jun 17, 2011 at 18:06
  • \$\begingroup\$ Did you find a good deal on flash-caps? I've been looking for them. \$\endgroup\$
    – Connor Wolf
    Jun 18, 2011 at 8:06
  • \$\begingroup\$ @Fake Name - nothing special - got few Russian K50-17 ones (designed for flashlights, but not good enough to look for them), and lots of usual JAMICON 450V ones - these are not designed for pulse discharge, so I will have to pray. At least I will have lots of these jamicons in parallel, so probably they would not blow up :-D \$\endgroup\$
    – BarsMonster
    Jun 18, 2011 at 23:03
  • \$\begingroup\$ My problem is that usual flash bulbs are for lower voltage, somewhere at 200-300V, my lamps needs up to 1000 (500V gives much longer pulses with lower intensity), so not much of a choose on a market. \$\endgroup\$
    – BarsMonster
    Jun 18, 2011 at 23:05

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.