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Transformer on a (quasi)DC line

Discussion in 'General Electronics' started by PiRho Tech, May 2, 2004.

  1. PiRho Tech

    PiRho Tech Guest

    I'm wondering: Would it work to rectify 120v ac before dropping it into a
    transformer?
    Reason: my output is 13.8v, and I'd hate to lose 10% (especially when
    running ~15A) just to rectify it on the side of the secondary.
    I'm thinking it should work: You'd have a 120Hz ac, just raised by ~60v,
    di/dt would still be present to induce a field.

    Any thoughts?

    Mark D.
     
  2. Robert Baer

    Robert Baer Guest

    Me thinks that you should *learn* about some electronics before you
    put your tongue into the AC power outlet...
     
  3. Some Guy

    Some Guy Guest

    Silly.

    First, you aren't talking about rectifying here, if you will still have
    120vac floating on a 60vdc level... that's called adding a dc offset.
    Rectifying either cancels or inverts half of the wave.

    Second, if you did put 120vac floating on 60vdc into a transformer, the
    effect would be: The transformer would perform exactly as it did before you
    added the dc offset, except that it would also GET HOT. The output would be
    exactly the same as it would have been without the offset. At least until
    the transformer got hot enough from the 60vdc to melt...

    On the other hand, if you did rectify the ac, then effectively you would be
    putting half the voltage into the transformer, and altering the input
    waveshape to boot. This would have the effect of halving the output
    voltage, and causing voltage spikes on the output which might just destroy
    the components on the output side...

    The other guy is right. You should pick up a TEXTBOOK (not just something
    off the shelf at Barns n Nobles) on electronics, and read through the
    chapter on how transformers work.
     
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