Rectified mains question

Discussion in 'General Electronics Chat' started by oidium45, Aug 31, 2011.

  1. oidium45

    Thread Starter Active Member

    Apr 24, 2010
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    I have a stupid question but I cannot seem to find the answer online. Everyone keeps telling me that rectified mains voltage (120vac) is 180vdc..
    According to the math (assuming that mains is 120v and not 110v) It is more like 170vdc. Correct me if I am wrong here.

    Vp=Vrms x (square root of 2)
    Does a filter Capacitor after the full bridge rectifier make it 180vdc?
     
  2. tom66

    Senior Member

    May 9, 2009
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    The actual range (from 100VAC - 127VAC) is 141.2V to 179.6V. So "140V" to "180V" is about right. Nominal voltage is 160-170V.
     
  3. t06afre

    AAC Fanatic!

    May 11, 2009
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    Yes I would say you are correct 120x(square root of 2) is more like 170 volt than 180 volt. And the rectifier will also cause some voltage drop. So we may be talking perhaps closer to 165 volt.
     
  4. #12

    Expert

    Nov 30, 2010
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    One more point...the capacitor will not boost the voltage. It will charge to Vpeak minus Vrectifier(s) then sag (under load) until the next power line peak happens. In Cally-forn-ya, thats one 60th of a second later for a simple rectifier and one 120th of a second for a full wave rectifier.

    I'm talking absolute here. No fudge factors.
     
  5. #12

    Expert

    Nov 30, 2010
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    For a sine wave, volts peak = volts rms times the square root of 2.

    I don't even know how you got a dc term into the equasion.
     
  6. t06afre

    AAC Fanatic!

    May 11, 2009
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    The OP wrote
    Which I would consider correct. So I can not see anything wrong wrong in the OP argumentation
     
  7. #12

    Expert

    Nov 30, 2010
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    Ionic had a post in between what is now post 4 and post 5. That is why you can't see who I was talking to.
     
  8. t06afre

    AAC Fanatic!

    May 11, 2009
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    I see. I was somewhat puzzled by your post. But now I understand.
     
  9. oidium45

    Thread Starter Active Member

    Apr 24, 2010
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    Thank you gentlemen I appreciate your input. It would appear that I was correct and was simply misinformed.
     
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