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Back EMF

  1. Sep 23, 2010 #1
    I have always wondered if anyone has ever developed an understanding of why Back EMF happens?

    All I know is it happens when the the field inside of a transformer collapses at some low frequency during the collapse of the coil when the transistor shuts off creates a huge spike hundreds of times the supply voltage is created within the coil. is there a new understanding of why this happens?

    I appreciate any help in in expanding my knowledge of this phenomena.

  2. jcsd
  3. Sep 23, 2010 #2


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    If I'm not mistaken, it is because the electromagnetic field of the transformer actually stores energy, and when you shutoff the transformer, the electromagnetic field collapses, sending that energy back as a spike of power.
  4. Sep 23, 2010 #3
    Remember also, that back EMF collapse, regardless of high voltage or not, has a power factor slightly less than that which created it.
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