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The same tired quesiton about rectification

Discussion in 'General Electronics Chat' started by Kal_B, Sep 1, 2017.

  1. Kal_B

    Kal_B Member

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    Hello everyone,


    I don't know why I still don't get this maybe the formulas are too complicated.

    I have 230VAC which I will connect to full wave rectifier, what would the output be without any filters or anything else connected.

    I found answers ranging from 230 x 1.414 to 230 x 0.7 and many other formulas.


    Thanks
    Kal
     
  2. Pommie

    Pommie Well-Known Member Most Helpful Member

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    Without a capacitor it will be 230V DC but very bumpy. The bumps will go from 0V to 230*1.414 - the peak voltage. With a capacitor, it will charge to the peak voltage - 230 * 1.414. The 1.414 is the square root of 2.

    edit, the 0.707 you've encountered is one over root two and is how you convert the other way.

    Mike.
     
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  3. Kal_B

    Kal_B Member

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    Thanks Mike.

    To clarify, and please excuse my ignorance, the bumps will go from 0V to 325V that is DC with a ripple?

    Thanks
    Kal
     
  4. dave

    Dave New Member

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  5. crutschow

    crutschow Well-Known Member Most Helpful Member

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    Yes, you have a 325V ripple.
    The RMS value of this is still 230V.
    The average DC value of this is 0.636 of the peak or 207V.
     
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  6. Kal_B

    Kal_B Member

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    What would the frequency of the ripple, does it relate to the frequency of the AC current rectified so if it's 60HZ then the ripple will be at the same rate?

    Thanks
    Kal
     
  7. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Full wave rectification doubles the ripple frequency, so 120Hz for 60Hz mains.
     
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  8. crutschow

    crutschow Well-Known Member Most Helpful Member

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    Here's a simulation to show the output from a full-wave rectified output for a 230Vac, 60Hz input (yellow trace).
    Note that the output ripple is double the input frequency as Nigel noted, and that the average (DC) output is 204.75V and the RMS output is 227.4V (slightly less than I stated in post #4 due to the forward voltage drop loss of the diodes).

    upload_2017-9-4_8-33-43.png
     
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  9. JonSea

    JonSea Well-Known Member

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    Here's a more conventional picture of a bridge rectifier circuit. It's easier to trace what happens when the sine wave is positive or negative.

    SmartSelectImage_2017-09-04-09-26-28.png
     
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