Responding in another old thread:
... < snippage >
The power supply I'll be building will be used to power a coil gun or
another magnetic pulse generator. So I should just look for capacitors
with a low enough internal resistance to fully discharge fast enough
for my application?
I'm pretty sure there IS a maximum pulse current you can do without
damaging the cap, and it's less than you would be doing in this
application (less than the max voltage divided by ESR). The ripple
current rating is for limiting heat (full-time ripple current across
ESR causes the cap to heat up), and so it stands to reason that a
pulse rating (which is very intermittent) would be substantially
higher. But since "ordinary" electrolytics are rarely used in such
high-pulse-current applications, manufacturers don't take the time to
test and characterize them for such a rating. Xenon flash is such an
app which uses special caps designed for it, but they may not be
available in the capacitance/voltage rating you want for your app.
From my reading (ISTR at the site below, and maybe the quarter
shrinker site), even "pulse rated" capacitors are rated for a fixed
number of pulses and don't work as well after having given many
high-current discharges.
Sign up on
http://www.4hv.org - they've used "regular" caps for
these applications. ISTR reading that electrolytics' life is reduced,
but are still usable for this. That's a great site for this stuff
(coil guns and similar things), it appears to have a high
concentration of people with a lot of knowledge in this area.
Be sure to ask the right questions in the right forum. Even though
your app for such a cap is a coil gun (which is discussed in The
"Electromagnetic Projectile Accelerators" forum), you're asking about
an electronic component (capacitor) so this goes in the "General
Science and Electronics" forum. I actually didn't make this mistake
myself, I learned it by lurking and seeing someone else get corrected
on it. I think the site makes this a little less clear than it should
be, perhaps I should mention something about it over there.