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Dependence of damping constant on current

  1. Sep 16, 2015 #1
    Using an eddy current brake, one would expect the damping constant ##δ## to increase with the current ##I## supplied to the eddy current brake. My question is, why is ##δ## proportional to ##I^2## and not merely ##I##?

    The magnitude of the eddy current is ##\frac{1}{R}\frac{dΦ}{dt}##, which is why I initially thought ##δ## was proportional to ##I##, because the induced current is proportional to ##\frac{dΦ}{dt}##.

    P.S: This link http://home.uni-leipzig.de/prakphys/pdf/VersucheIPSP/Mechanics/M-17E-AUF.pdf
    was what I used as reference; it stated the relation but does not seem to explain why.
     
  2. jcsd
  3. Sep 17, 2015 #2

    Hesch

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    Gold Member

    The B1-field induced by the brake is proportional to I.
    The induced eddy voltage in the disk is proportional to the B1-field.
    The induced eddy current in the disk is proportional to the eddy voltage.
    The induced B2-field from the disk is proportional to the eddy current.
    The braking force is proportional to the magnetic energy density in the airgap = ½*B1*(B20) [ J/m3 ].

    That's why.
     
    Last edited: Sep 17, 2015
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