Capacitors

[Mike]

Am I right in thinking that it's the ripple current property of a capacitor
that makes it suitable for discharge experiments? When I say discharge
experiments I mean discharging the capacitor as quickly as possible (e.g.
coilguns, railguns etc etc). Should the ripple current be as high as
possible (e.g. 5A is better than 4A)?

I've seen some capacitors, which are described as suitable for discharge and
pulse applications. But the ripple current seems to be smaller than other
standard capacitors (of the same size and voltage). The capacitor has the
following specs:

400V
1000uF
Ripple Current 4.05A

Here's the data sheet of the capacitor if anyone's interested:

http://www.farnell.com/datasheets/7958.pdf

Any ideas?

 

[John Popelish]

Mike wrote:

Am I right in thinking that it's the ripple current property of a capacitor
that makes it suitable for discharge experiments? When I say discharge
experiments I mean discharging the capacitor as quickly as possible (e.g.
coilguns, railguns etc etc). Should the ripple current be as high as
possible (e.g. 5A is better than 4A)?

There are (at least) two important aspects of a caps ripple current
rating. One involves how much internal resistance the capacitor has
that generates heat as ripple current passes through it. The other is
the capacitor's ability to get rid of this heat through its surface
and its ability to handle the internal temperature rise this process
requires. But if all other properties were exactly the same, it is a
pretty safe bet that the one rated for higher ripple current would
stand a rapid discharge process better.

I've seen some capacitors, which are described as suitable for discharge and
pulse applications. But the ripple current seems to be smaller than other
standard capacitors (of the same size and voltage). The capacitor has the
following specs:

400V
1000uF
Ripple Current 4.05A

It looks suitable for some rate of discharge to me. ;-)

Here's the data sheet of the capacitor if anyone's interested:

http://www.farnell.com/datasheets/7958.pdf

Any ideas?

Have you calculates what RMS ripple current (over a full cycle time)
your circuit will produce? Maybe it is way more or less than these
specs and you are worrying about nothing or way off base. Start with
what you need.

The ultimate specification for rapid discharge applications is fusing
current. This is the I^2*T that will melt the internal current path
somewhere. When you find one with this kind of spec, you know they
designed it for big pulses.
--
John Popelish