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# RE: [femm] Transient Magnetic Field Analysis

- To: <femm@yahoogroups.com>
- Subject: RE: [femm] Transient Magnetic Field Analysis
- From: "Wellington Koepsel" <wkoepsel@worldnet.att.net>
- Date: Sat, 7 Jun 2003 19:59:18 -0700
- Importance: Normal
- In-reply-to: <bbgish+s5jr@eGroups.com>

    Rather than using a series of frequencies to simulate the step. You might do
    an FFT of a periodic square wave and use the amplitudes at the respective
    frequencies as the driving force for the transient response. Admittedly the
    step consists of all frequencies however the amplitudes are not all the
    same. In order to realize a reasonable response the amplitudes must be taken
    into account. A periodic square wave will only have odd harmonics and the
    amplitudes will decrease as a function of 1/n. The square wave is reasonably
    represented up to the ninth harmonic. Your results may depend on the average
    value of the square wave if so it can be included. The harmonics do not
    change.
    W. W. Koepsel, wkoepsel@ieee.org

    -----Original Message-----
    From: mjcraft78 [mailto:mjcraft78@yahoo.com]
    Sent: Monday, June 02, 2003 3:25 PM
    To: femm@yahoogroups.com
    Subject: [femm] Transient Magnetic Field Analysis

    I am attempting to model the magnetic field of an electromagnet with a
    step input of current to the coil (this is an axisymmetric problem).
    I understand that FEMM can model the effect of eddy currents &
    hysteretic losses on a "magnetic circuit" for a given frequency, but
    currently does not have the capability of modeling a DC bias. Is
    there some way that I could correlate the AC response at several
    different frequencies to predict the behavior for a step input?
    Additionally, I've used FEMM to calculate the inductance of the
    circuit, but I'm guessing that this does not take into account the
    generation of eddy currents due the rate of change of the field?
    Please let me know if I'm way off here or what I can do to model this
    problem accurately.

    Thanks for your help,

    Mike Craft

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- References:
  - Transient Magnetic Field Analysis
    - From: "mjcraft78" <mjcraft78@yahoo.com>

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