rated ripple current

Discussion in 'General Electronics Chat' started by StephenDJ, Dec 23, 2008.

  1. StephenDJ

    Thread Starter Active Member

    May 31, 2008
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    I'm looking for caps. Ideally, should the rated ripple current be a higher or a lower value? I know the tan o and impedence should both ideally be a low value. But what about the rated ripple current? Which is ideal? rated ripple a good or bad thing?
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    I guess you are talking about a DC power supply filter. Ideally the ripple current should be 0. Ripple current is not good, it causes losses in the transformer windings and more power dissipation.
     
  3. StephenDJ

    Thread Starter Active Member

    May 31, 2008
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    Thanks. I was mainly reffering to the capacitors as advertised. So I assume that, while I don't know how these caps are measured by the manufacturer to get a rating, the ones with lower rated ripple are best. (Say, doesn't the applied voltage influence this current? if so, then how is it that the manufacturer can give a CONSTANT rating?)
     
  4. mik3

    Senior Member

    Feb 4, 2008
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    Ohhh, I was talking about another think (i had in my mind the ripple voltage of the DC power supplies). The rated ripple current of a capacitor is fixed and is the amount of current the capacitor can conduct without get destroyed (overheat). The greater the rated ripple current the more current the capacitor can conduct. It is a fixed value but the current in the circuit, where you will use the capacitor, depends upon the frequency and the voltage.
     
  5. StephenDJ

    Thread Starter Active Member

    May 31, 2008
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    Oh, I see. It's just a property of the capactor alone, and so it's fixed. So let me get this straight: I understand that ripple needs to be minimized in dc supplies. However, it's not LESS rated ripple current that I need in my caps, but it's MORE. Correct?
     
  6. mik3

    Senior Member

    Feb 4, 2008
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    You have to use a capacitor with a rated ripple current equal or greater than the ripple current the design is calculated to produce.
     
  7. StephenDJ

    Thread Starter Active Member

    May 31, 2008
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    Whew, I'm all clear now. Thanks for clearing up my question. I now have the knowledge to choose my caps wisely, and that my caps should be able to handle the current from now on. Thanks.
     
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