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# Re: ac current

- To: femm@yahoogroups.com
- Subject: Re: ac current
- From: "David Meeker" <dmeeker@ieee.org>
- Date: Fri, 03 Oct 2003 13:42:41 -0000
- In-reply-to: <blfu80+ovoc@eGroups.com>
- User-agent: eGroups-EW/0.82

    --- In femm@yahoogroups.com, "ahmad_m_eid" <ahmad_m_eid@y...> wrote:
    > Dear all
    >
    > How to apply ac current to the coils in linear machine?
    > If it is discussed before, please direct me to the message.
    >
    > thanks
    >
    > ahmad

    If you want to run AC currents, you can just specify a frequency other
    than zero in the problem definition. For AC problems, all quantities
    are represented as complex values. These complex values can be mapped
    back onto the time domain using the relationship (for example, with
    current density J):

    J[t] = Re[J*Exp[j*omega*t]]
    = Re[J]*Cos[omega*t] - Im[J]*Sin[omega*t]

    So if you have a specific for of J as a function of time that you want
    to put into the coils, you pick the real and imaginary parts of J on
    the basis of the above to give you the desired current amplitude and
    phase.

    If you want to do magnetostatic simulations that are looking at a
    series of particular instants at which the shuttle in you linear motor
    has a series of different positions, you'd want to write a lua script
    to move the shuttle and set the instantaneous current on the basis of
    the current position.

    Dave.

- References:
  - ac current
    - From: "ahmad_m_eid" <ahmad_m_eid@yahoo.com>

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