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Homework Help: Foucault currents / Eddy Currents vs material selection

  1. Dec 6, 2009 #1
    Hello, I am a mechanical engineer by education and I am working on a multi disciplinary problem. I regularly work with eddy current dynamometers at work and I am curious about the materials used within the rotor and stator of these dynamometers.

    First off, this isn't a homework problem per se. I am not enrolled in a University and I am not trying to get the answer to this question for credit. However, I have a suspicion that the chart I am looking for is in a textbook somewhere, so I thought this would be a good place to start. Please let me know if I should move this to a different forum.

    Ok, so here is what I think I know. An eddy current dynamometer uses a spinning rotor shaft attached to the engine/drive train of the device you want to test. The stator may be a disk with gaps across the face and a coil wound around the disk to create a magnetic field. (Some stators are electromagnets positioned at the face of the rotor, rather than wrapped.) The gaps carry less magnetic flux to the rotor, causing a change in magnetic field as the rotor face sweeps past the stator face. The periods of high/low magnetic field induces an eddy current in the rotor as it spins, creating heat and causing the rotor to absorb power created by the drive train. Equal and opposite reaction creates a torque on the stator, which is measured with a load cell.

    So here are my questions,

    Ignoring thermodynamic and mechanical properties, what is the ideal rotor material? (Ideal meaning the material which absorbs the most power from the drivetrain given that everything else is constant (electromagnet current/rotor stator gap/rotational speed) Is this the material with the lowest resistance (ohms)?

    Has anyone seen a textbook somewhere that ranks a list of engineering materials from most eddy currents produced to least? (Please include the ISBN number if you know of a book)

    Are there equations for calcualting the Foucault currents beyond what I have found in wikipedia?


    I am thinking about building an IZOD type apperatus for testing different materials. Somethign with a swinging electromagnet passed the stationary test material. I would be able to compare materials by energy lost in the pendulum as the magnet passes the test material. This would allow me to vary gap, magnetic flux, material, material thickness, etc. However, if this information can be calculated or I can look on a chart I wouldn't need to reproduce the test. Has anyone seen something like this?
    Last edited: Dec 6, 2009
  2. jcsd
  3. Jul 23, 2017 #2
    hi, I'm also had same problem with you. do you already get the answer?
  4. Jul 24, 2017 #3

    jim mcnamara

    User Avatar

    Staff: Mentor

    @ibrahim28 - these are old unanswered questions put out so you can practice on them. They do not have an answer stashed away somewhere. Also, please note the date the question was asked - 7 years ago.
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