Centre Tap Transformer Question

Discussion in 'Homework Help' started by Zaraphrax, Sep 3, 2009.

  1. Zaraphrax

    Thread Starter Active Member

    Mar 21, 2009
    47
    3
    Hi there,

    I'd appreciate if you could check my answer. I only require a simple "right" or "wrong". Thanks.

    I need to determine the ripple peak to peak voltage and the average voltage for this transformer, that has a 100 ohm load connected. Voltages supplied are RMS values.

    [​IMG]



    Here's what I've done:

    Time constant on capacitor: CR= (100 x 10^-6) x 100 = 10ms

    Since RMS voltages are supplied, 12 * (2^0.5) = ~17V

    Plotting the output of the circuit (and the capacitor discharge curve), I determined that the average voltage was about 14.5V (~12V minimum to 17V), with a ripple of 5 V.

    Is this correct?

    Thanks.
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
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    I have not checked your numbers. But did you use 50 or 100 Hz then you calculated the ripple? You use a full wave rectifier and then you have to use mains frequencyX2
     
  3. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    If you assume that the ripple voltage is small then it can be approximated by a triangular wave.

    Thus the ripple frequency is:

    Vripple=Vaverage/(2fCR)

    Vaverage=Vmax-Vr/2

    by using the two above equations you get:

    Vaverage=Vmax/[1+1/(4fCR)]

    f=mains frequency

    Check your results.
     
  4. t06afre

    AAC Fanatic!

    May 11, 2009
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  5. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    The link does not work. The forum does not work with links that end on ")".
    The "(" can be replaced with %28
    The ")" can be replaced with %29

    Here is the link that works:
    http://en.wikipedia.org/wiki/Ripple_(electrical)

    Greetings,
    Bertus
     
  6. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
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    Ouch;) so much for copy and paste Well anyway the link is now correct. So read it and learn
     
  7. Zaraphrax

    Thread Starter Active Member

    Mar 21, 2009
    47
    3
    Thanks guys. The question actually doesn't give a mains frequency, so I'll just assume 50hz since thats what our main is over here. Thanks.
     
  8. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The output voltage will be higher than is calculated since the load current is so low.
     
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