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# Re: [femm] help

- To: femm@yahoogroups.com
- Subject: Re: [femm] help
- From: David Meeker <dmeeker@foster-miller.com>
- Date: Wed, 26 Sep 2001 17:14:44 -0400
- Organization: Foster-Miller, Inc.
- References: <F144IiGXix4A2DreBBs0000ae5f@hotmail.com>

    mercedes sampere wrote:

    > David,
    > I'm searching on dispersion reactance for induction motors, so actually I'm
    > interested about self inductance but I calculate mutual inductance in order
    > to have an idea if the model is OK.
    > I took the model for this motor from a design handbook and that's why I
    > think I'm doing something wrong, because it doesn't make sence that self
    > inductance would be greater than mutual inductance for a motor, unless it is
    > not properly designed.
    > You're right about coils, what do I have to do to drive them in series?
    > About current, in the original model stator current was 88.8 A but I've
    > increased it to see if I could get less leakage.
    > These are motor features:
    > Usefull power: 81kW
    > Tension: 380/660V
    > Synchronous speed: 1500rpm
    > Frecuency: 50Hz
    > Number of phases: 3
    > 2 pairs of poles
    > Power factor: 0.89
    > Sliding coefficient: 0.0133
    > Current per phase(stator): 88.8 A
    > Number of slots(stator): 48
    > Current per phase(rotor): 377 A
    > Number of slots(rotor): 36
    >
    > Should I get better results if I model the hole geometry (I mean not only
    > two slots)?
    >
    > Thank you very much
    > Excuse my english
    >
    > Mercedes
    >

    I think when you say "dispersion reactance" that you mean what I'd think of as
    "leakage reactance." What you need to model depends sort of on what you are
    trying to get. If you are just interested in slot leakage, you'd probably do
    well enough by just modeling the inside of a slot, applying an A=0 boundary
    condition across the slot opening an a dA/dn boundary condition (which gets
    applied by default if you don't specify anything) to the slot walls. Then, you
    don't have to model any of the core at all. You can then get the slot leakage
    inductance via the magnetic field energy.

    On the other hand, if you really want the mutual inductance between the stator
    and rotor, you have to end up modeling at least a pole's worth of the machine
    (and applying appropriate periodic boundary conditions).

    Dave.

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    Content-Transfer-Encoding: 7bit

    <!doctype html public "-//w3c//dtd html 4.0 transitional//en">
    <html>
    mercedes sampere wrote:
    <blockquote TYPE=CITE>David,
    <br>I'm searching on dispersion reactance for induction motors, so actually
    I'm
    <br>interested about self inductance but I calculate mutual inductance
    in order
    <br>to have an idea if the model is OK.
    <br>I took the model for this motor from a design handbook and that's why
    I
    <br>think I'm doing something wrong, because it doesn't make sence that
    self
    <br>inductance would be greater than mutual inductance for a motor, unless
    it is
    <br>not properly designed.
    <br>You're right about coils, what do I have to do to drive them in series?
    <br>About current, in the original model stator current was 88.8 A but
    I've
    <br>increased it to see if I could get less leakage.
    <br>These are motor features:
    <br>Usefull power: 81kW
    <br>Tension: 380/660V
    <br>Synchronous speed: 1500rpm
    <br>Frecuency: 50Hz
    <br>Number of phases: 3
    <br>2 pairs of poles
    <br>Power factor: 0.89
    <br>Sliding coefficient: 0.0133
    <br>Current per phase(stator): 88.8 A
    <br>Number of slots(stator): 48
    <br>Current per phase(rotor): 377 A
    <br>Number of slots(rotor): 36
    <p>Should I get better results if I model the hole geometry (I mean not
    only
    <br>two slots)?
    <p>Thank you very much
    <br>Excuse my english
    <p>Mercedes
    <br><a href="http://docs.yahoo.com/info/terms/";></a>&nbsp;</blockquote>
    I think when you say "dispersion reactance" that you mean what I'd think
    of as "leakage reactance."&nbsp; What you need to model depends sort of
    on what you are trying to get.&nbsp; If you are just interested in slot
    leakage, you'd probably do well enough by just modeling the inside of a
    slot, applying an A=0 boundary condition across the slot opening an a dA/dn
    boundary condition (which gets applied by default if you don't specify
    anything) to the slot walls.&nbsp; Then, you don't have to model any of
    the core at all.&nbsp; You can then get the slot leakage inductance via
    the magnetic field energy.
    <p>On the other hand, if you really want the mutual inductance between
    the stator and rotor, you have to end up modeling at least a pole's worth
    of the machine (and applying appropriate periodic boundary conditions).
    <p>Dave.
    <br>&nbsp;</html>

    --------------A1B3FAE31969430F061B5E66--

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    org:Foster-Miller, Inc.;Electrical and Electronic Systems Group
    version:2.1
    email;internet:dmeeker@foster-miller.com
    title:Senior Engineer
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    fn:David Meeker, Ph.D.
    end:vcard

- References:
  - Re: [femm] help
    - From: "mercedes sampere" <m_veinti2@hotmail.com>

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