Primary capacitors - general question

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  • Majestyk
    Senior Member
    • Nov 2013
    • 96
    • Germany
    #1

    Primary capacitors - general question

    Hello everybody,

    accordig to the datasheets capacitors with for example 470uF, a voltage rating of 400V and 85°C are typically able to stand a ripple current of about 3.5A
    A similar capacitor for 105°C can only stand a ripple of about 2.5A.
    It seems to be impossible to produce a capacitor that would have both a high temperature rating and high ripple capabilities at the same time.

    Of course everybody would prefer the 105° cap as a replacement.
    My question is: Could there be a need for a rating of 3.5A ripple in ATX PSUs after the bridge-rectifier and could this be the reason why many PSUs are equipped with 85° primary filtercaps?
    Tags: None
    • SM-Piyes90
      Senior Member
      • Feb 2014
      • 120
      • Morocco
      #2
      Re: Primary capacitors - general question

      Don't know if this sounds correct but i guess when the temp goes up , current decreases with . So it impossible to have both parameters high

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