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Magnetic hysteresis loop area meaning

  1. Sep 11, 2015 #1
    Let's consider the Magnetic hysteresis loop of a certain material: this is an example. In many sites and books it is written that its area is proportional to the energy wasted as heat, so [itex]A = kE_d[/itex].
    In particular, that area "is related to the amount of energy dissipation upon reversal of the field" (this is the source). I would like to ask some clarifications:

    1) When exactly is that energy dissipated? When the impressed magnetic field [itex]\mathbf{H}[/itex] decreases from the saturation point or when [itex]\mathbf{H}[/itex] increases till the saturation point?
    2) How can be circuitally represented that energy dissipation in the circuit of a transformer like this?
    3) Maybe [itex]E_d[/itex] can be obtained as an integral. If [itex]A = kE_d[/itex], what are the steps needed to mathematically show this result and which is the meaning of [itex]k[/itex]? (If a link is more convenient than directly typing the steps, it would be excellent as well)
    I can't see how dimensionally can be obtained an energy quantity (Joule) from A/m ([itex]\mathbf{H}[/itex]) and from Tesla ([itex]\mathbf{B}[/itex]).
  2. jcsd
  3. Sep 11, 2015 #2


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    Gold Member

    Magnetic energy density ( Ed ) = ½*B*H [ J/m3 ]. So Ed = 0 in b, c, e, f in the attached figure and has a max value i a, d.

    If the area of the hysterisis curve = 0, no energy will be dissipated as per cycle.

    Units: B*H = [N/(Am)] * [ A/m ] = [ N/m2 ] = Nm/m3 = [ J/m3 ]
  4. Oct 7, 2015 #3
    Thank you!
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