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Eddy current loss help please

  1. Oct 5, 2013 #1
    Hi, I have been trying to understand eddy current loss in transformer cores but seem to have run into a bit of a misunderstanding with one of the books I have read, and I was wondering if someone could just clarify if I have got this all right.

    starting with the beginning, if the magnetic flux varies sinusoidal, then the flux at one instant would be;

    ∅ = ∅msin(ωt) (I have been told this should be done in degrees and not radians?)

    value of induced emf in core at any time (t) =

    [itex]\frac{d∅}{dt}[/itex] = ω∅mcos(ωt)

    Am I correct in saying that from this second equation, ωθm = Em (Max induced EMF in core)?

    If Es = rms value of emf induced in core, this = [itex]\frac{1}{\sqrt{2}}[/itex]ω∅m = [itex]\sqrt{2}[/itex]∏f∅m = [itex]\sqrt{2}[/itex]∏f(ABm)

    Eddy current Power Losses = [itex]\frac{Es2}{Rs}[/itex]
    = [itex]\frac{2*∏2*f2*A2*Bm2}{Rs}[/itex]

    The next bit is the section of the notes that seems to confuse me,

    Eddy current Power Loss = PE = KE*f2*BM2, where KE = Constant = 2*∏2*A2/Rs.

    The book then says 'hence eddy current losses = α (f2*BM2)

    Does this mean that KE is the same as α and eddy current power loss is the same as eddy current loss, or are these two different things? As far as I can see they appear the same but I just wanted to make sure from someone who has a bit more experience or knowledge of this.

  2. jcsd
  3. Oct 6, 2013 #2


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    Staff: Mentor

    That would be emf induced per turn in the winding around the core, I think.

    Lose the equals sign. I think that should be a simple proportionality:

    eddy current losses α (f2*BM2)
  4. Oct 7, 2013 #3
    Both are the same, eddy current losses means the power loss due to eddy current.
  5. Oct 8, 2013 #4

    jim hardy

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    Science Advisor
    Gold Member

    Try a search on Steinmetz - he figured it out by experiment late 1800's
    some old textbooks are showing up online nowadays with first-hand explanation.
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