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A very simple electrical AC generator can be made by spinning magnets around a fixed stator coil. The changing magnetic field induces current in the stator winding.

It would seem that at a fixed frequency, this system is best modeled as a current source with some series resistance and inductance. Is this a good model?

If so, it would suggest that the behavior of the system in an open-circuit scenario would be to generate a very high voltage at the output pins with zero current flow. Conversely, in a short circuit scenario, it would run a fixed amount of current through the loop which would be dissipated as heat in the series resistance (stator wires).

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  • \$\begingroup\$ Change in magnetic field induces a voltage as per Maxwell's equations. See the third equation in the table. \$\endgroup\$
    – AJN
    Commented May 13, 2021 at 16:44
  • \$\begingroup\$ @AJN, so more of a voltage source with series inductance and resistance? \$\endgroup\$
    – user8908459
    Commented May 13, 2021 at 17:02
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    \$\begingroup\$ That seems correct. Inductance would be larger than resistance. And since a short-circuit has high voltage over low impedance means large current, which will damage generator. Same for an AC motor. \$\endgroup\$
    – StainlessSteelRat
    Commented May 13, 2021 at 17:24
  • \$\begingroup\$ No - it is a VOLTAGE source with series resistance and inductance. A current source would give infinite voltage on no-load. \$\endgroup\$
    – Kevin White
    Commented May 13, 2021 at 18:48
  • \$\begingroup\$ Yes, voltage source. I swear I read voltage source. \$\endgroup\$
    – StainlessSteelRat
    Commented May 13, 2021 at 21:58

3 Answers 3

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It is generally accepted that synchronous machines are modeled as a sinusoidal voltage source in series with a synchronous reactance, Xs in series with an armature resistance, Ra. A line-to-neutral model of one phase of a three-phase machines is used to analyze a 3-phase machine.

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It would seem that at a fixed frequency, this system is best modeled as a current source with some series resistance and inductance. Is this a good model?

No, that's a very naïve model. A current source in series with anything is still just a current source. A voltage source is made "practical" with series elements (such as R and L) but, a current source is modelled with parallel elements to make it useful.

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    \$\begingroup\$ C'mon. It's probably a typo. The OP meant (or will mean, soon) a voltage source with a series impedance, or a current source with a parallel impedance. \$\endgroup\$
    – TimWescott
    Commented May 13, 2021 at 18:46
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If you are using modeling software that handles mutual inductance, try a mutual pair of inductors and drive one with a sinusoidal voltage. Use the other for an output.

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