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# [femm] Re: lamination core losses

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- Subject: [femm] Re: lamination core losses
- From: Dcm3c@aol.com
- Date: Thu, 9 Mar 2000 20:09:45 EST
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    In a message dated 3/8/00 5:37:02 PM Eastern Standard Time,
    pvallian@central.ntua.gr writes:

    > how can i calculate a motor's core losses??
    > i have the specific losses for the material

    Hmm--good question. An approximate way that would get you into the right
    ballpark is to note that if the materials were linear (perhaps with some
    hysteresis that could be described as a simple phase lag), the losses at any
    point would scale with B^2. If this were true, you could find the
    root-mean-square flux density in the core of your machine and pick the point
    of your spec sheet corresponding to Brms at the frequency of interest. They
    usually give losses in Watts/lb (or perhaps Watts/Kg in parts of the world
    that know how to handle SI units), so to get the total loss, just multiply
    Watts/mass by the mass of the stator. Like I say, this is sort of rough, but
    it ought to get you pretty close.

    A second way is to define the lamination properties in the Block Properties
    dialog corresponding to your material fully. Pick a lamination fill factor
    (1 isn't realistic; 0.9-0.95 might be more so; it depends on your lamination
    thickness and construction methods) and lamination thickness. Define a
    non-zero conductivity, so that eddy current effects are represented. Pick a
    reasonable hysteresis angle to include represent hysteresis losses. Then,
    evaluate the problem, and take the block integral of "hysteresis and/or
    laminated eddy current losses" over the volume of the core. This includes
    the effect that the hysteresis and eddy currents have on the field
    distribution, which can change flux levels and therefore losses. The down
    side of this method is that it uses sort of an overly simplistic material
    model--linear BH curve and hysteresis represented by a frequency- and
    amplitude-independent phase lag. However, with a little head scratching, you
    may be able to back out values for permeability, hysteresis lag, and
    conductivity that reproduce the manufacturer's loss curves relatively well,
    implying that good results might be obtained by this method.

    Dave.
    --
    http://members.aol.com/dcm3c

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