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capacitor

Discussion in 'General Electronics Discussion' started by thedoc8, Oct 3, 2013.

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  1. thedoc8

    thedoc8

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    Oct 3, 2013
    I have been looking for a formula to calculate the charge time of capacitor. Not the 5 time constant formula. Example say I have a .ooo5 cap across 24vac supply 60hz, I need to figure how much time of the half cycle it will take to fully charge. No resisitor. Any formulas...? Thanks
     
  2. duke37

    duke37

    5,364
    772
    Jan 9, 2011
    If it is connected directly across the supply when at zero voltage without resistance, then it will be fully charged in a quarter of a cycle.
     
  3. thedoc8

    thedoc8

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    Oct 3, 2013
    Thanks duke, but I need the formula as I need it for several cap values from 1 to 4 mil second charge time and faster for 500khz
     
    Last edited: Oct 4, 2013
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    ...and fully discharged in the next quarter cycle (4.166667 milliseconds), and fully charged again in the opposite direction in the next quarter cycle, before being discharged again in the following quarter cycle.

    And all of that that repeats 60 times per second.
     
  5. thedoc8

    thedoc8

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    0
    Oct 3, 2013
    This I know, but say 500uf, is 4.1milliseconds long enough for full charge of the cap. I know the voltage is at Max but is it across the cap long enough for full charge. At much higher frequency the charge time is greatly redused. So is their a fourmula...?
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    Yes 1/(4f)

    Gives answer in seconds.

    It's pretty pointless though.

    Perhaps you could tell us why you want to know this. Then we can be possibly of some practical assistance.
     
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