Find the average voltage for a phase angle circuit

Discussion in 'Homework Help' started by cts_casemod, Nov 16, 2014.

  1. cts_casemod

    Thread Starter Member

    May 14, 2013
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    Hi all,

    Assume I have a triac and I wish to make a light dimmer as below:

    [​IMG]

    Now, assuming I trigger the triac at a given angle my RMS voltage will not equal Vpeak/sqroot(2) anymore. How can I calculate both the average and RMS output voltage in this case?

    [​IMG]

    Regards
     
    Last edited: Nov 16, 2014
  2. WBahn

    Moderator

    Mar 31, 2012
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    The same what that the Vpeak/sqrt(2) formula was found -- by applying the definition of RMS voltage.
     
  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    Pedantry on terminology. Probably unwise to interchange RMS with average.
     
  4. WBahn

    Moderator

    Mar 31, 2012
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    Very true. I caught the discrepancy between the title and the description in the post but then looked past the last use of average. Good catch.
     
  5. cts_casemod

    Thread Starter Member

    May 14, 2013
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    And that will be...?
     
  6. cts_casemod

    Thread Starter Member

    May 14, 2013
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    For the purpose I'm quite happy with any of the two, if someone is willing to make the effort explaining.
     
  7. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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  8. WBahn

    Moderator

    Mar 31, 2012
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    Okay, if you are quite happy with finding the average, then I'll give that one to you for free. The average is 0 V. Look at your graph. Is it not that case that for every time the voltage is at some positive value that it is later at a negative voltage of the same magnitude? Well, that averages out to zero.
     
  9. WBahn

    Moderator

    Mar 31, 2012
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    What is the definition of RMS voltage?
     
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