% ripple factor

Discussion in 'Homework Help' started by lynnfaiz, Dec 16, 2012.

  1. lynnfaiz

    Thread Starter New Member

    Dec 16, 2012
    29
    1
    I have an answer for these questions but do not have the solution steps from my supervisor. However, i manage to get the answer for i & ii. but my answer for iii is different to the one given.
    My work are written below. can anyone help to confirm if the answer i have is the correct one.

    Question:
    The 35 Vrms ac voltage Vs is derived from an ideal 60Hz main
    transformer. It is connected to a half-wave rectifier and a
    220μF capacitor to form a dc power supply. If the load RL
    draws an average current 0.15A, determine:
    i. the peak-to-peak capacitor ripple voltage Answer : Vr(pp) = 5.6V
    ii. the average or dc voltage across the load Answer : Vdc = 43.82V
    iii. the percentage ripple factor, %r. Answer : 12.8%

    iii) my solution steps
    with formular --> %r = [Vr(rms) /Vdc] x 100%.
    I calculated Vr(rms) = Idc/ (4√3 (60)(220u) = 1.64V
    and Vdc = Vm - (Idc/2fC) =43.82V
    So, the %r = 1.64 / 43.82 (100%) = 3.74%

    Thanking you guys in advance!
     
  2. lynnfaiz

    Thread Starter New Member

    Dec 16, 2012
    29
    1
    and back to same question -# ii,
    Since i have the anwer for Vr(p-p) = 5.68V, why cant i use the formular

    Vdc= Vm - 1/2 [Vr(p-p)] to get the Vdc ?
    my answer will be 46.65V
     
  3. #12

    Expert

    Nov 30, 2010
    16,345
    6,831
    I am very old and can not understand modern school speak, but I don't remember any 4 radical3's in the ripple formula. I also did not see accounting for the voltage loss in the rectifier.

    I believe your last formula is correct. (Vdc=Vm-1/2[Vr(p-p)]
     
    lynnfaiz likes this.
  4. lynnfaiz

    Thread Starter New Member

    Dec 16, 2012
    29
    1
    Thanks for your reply #12.
    I am not from the States. Ans English is my second language, so it's maybe myself that are not having a good English here ;)

    The Vdc= Vm - 1/2 [Vr(p-p)] doesn't get me the correct answer.
    I think it has something to do with the half-wave rectifier.

    Really appreciate if someone can help :)
     
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