Capacitors: ripple current vs maximum current capability for one discharge

Discussion in 'General Electronics Chat' started by matters_100, Apr 8, 2016.

  1. matters_100

    Thread Starter New Member

    Mar 30, 2016
    15
    0
    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
     
  2. Picbuster

    Member

    Dec 2, 2013
    373
    50
    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).
     
  3. matters_100

    Thread Starter New Member

    Mar 30, 2016
    15
    0
    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
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,086
    3,024
    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.
     
  5. shortbus

    AAC Fanatic!

    Sep 30, 2009
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