Hi,

For an electrolytic capacitor, is there an empirical relation between ripple current and the maximum yet safe current which can be drawn for dozens of miliseconds for a discharge application ? I mean without damaging the capacitor.
For example, if an electrolytic capacitor is rated for 30A ripple current at 120Hz/85°C, how much current can I continuously draw safely for 100ms ?
I suppose the limiting factors would be the heat generated and the connectors maximum current capability.

Thks

 

The delta voltage = (current x discharge time cap )/ capacitor
discharge time related to impedance from load.
delta voltage= top top value ripple
current draw from cap up its maximum stored energy (no coil in load).

 

I guess I haven't expressed myself clearly.

For example, if I have an application which requires 500A for 100ms only once every minute (assuming a capacitance large enough), would a low ESR electrolytic capacitor rated for 30A ripple current at 120Hz/85°C be able to handle the large current without damage ?

Thks

 

Have you looked closely at the capacitor specifications? I seem to recall seeing information like that - peak "instantaneous" current. I would think the manufacturers are the only ones likely to be able to answer your question.

I believe - but don't know - that capacitors can survive intermittent shorts. Stuff outside the capacitor lights up and vaporizes, but I think the capacitor is OK.

 

While not an electrolytic cap, they do make caps for this type of thing, called "pulse capacitors". https://www.google.com/search?q=pulse+capacitor&ie=utf-8&oe=utf-8

Then there are photo flash caps. https://www.google.com/search?q=photo+flash+capacitor&ie=utf-8&oe=utf-8