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Homework Help: Permeability in ferromagnetic material (AC)

  1. Jun 8, 2015 #1
    1. The problem statement, all variables and given/known data

    The following coil-wound core (core length = L , Gap length = lg, cross- sectional area = A , core permeability = only hysteresis graph is given, N = N turns) is driven by a Voltage source, is known that the current in the coil is 60hz AC.
    a13fig03.gif hys21-600x254.jpg
    (a.) the time -varying magnetic current
    (b.) the time -varying voltage
    (c.) the time -varying Magnetic flux (core and gap)
    (d.) Max current

    2. Relevant equations


    3. The attempt at a solution

    What I have done is to first calculate v(t) looking up the Bmax in the hysteresis loop, then I have substituted that value in the above equation v(t), then I have calculated the current using H=NI/L, again I got Hmax from the hysteresis loop in order to obtain Imax.
    I don´t know how to continue: how to express the flux and B in terms of t if the permeability is not a constant.
    Thank you for your help!
  2. jcsd
  3. Jun 9, 2015 #2
    varying permeability means varying inductance of the circuit and thus varying magnetizing current. If only hysteresis curve is given we should use it to determine nonlinear permeability and thus H and B field. We can take H field to be purely sinusoidal and thus determine not-so-perfect sinusoidal B field in-turn determining the flux.
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