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Reactance of a synchronous machine

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    Reactance of a synchronous machine

    The reactance of a synchronous machine depends upon:


    a. Applied voltage
    b. Leakage flux
    c. Degree of saturation of magnetic core
    e. Power factor of supply current
    f. Winding configuration

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    Quote Originally Posted by kcorpuz View Post
    The reactance of a synchronous machine depends upon:


    a. Applied voltage
    b. Leakage flux
    c. Degree of saturation of magnetic core
    e. Power factor of supply current
    f. Winding configuration
    I believe its the degree of saturation of magnetic core. this can be tested with open/shorted circuit test.

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  5. gchoquette is offline Junior Member Pro Subscriber
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    Quote Originally Posted by kcorpuz View Post
    The reactance of a synchronous machine depends upon:


    a. Applied voltage
    b. Leakage flux
    c. Degree of saturation of magnetic core
    e. Power factor of supply current
    f. Winding configuration
    In case of machines that have reconfigurable windings, e.g 277/480, certainly the Winding Configuration would have a direct effect on the inductance, therefore the reactance seen by an AC supply.

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    Quote Originally Posted by gchoquette View Post
    In case of machines that have reconfigurable windings, e.g 277/480, certainly the Winding Configuration would have a direct effect on the inductance, therefore the reactance seen by an AC supply.
    I can see that because the impedance of the wye motor connection should be greater than in the delta connection, therefore the reactance change! But the voltages also change... how significant ?

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  9. joeldjiogo is offline Junior Member Pro Subscriber
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    Reactance of a synchronous machine

    Quote Originally Posted by kcorpuz View Post
    The reactance of a synchronous machine depends upon:


    a. Applied voltage
    b. Leakage flux
    c. Degree of saturation of magnetic core
    e. Power factor of supply current
    f. Winding configuration

    considering the internal diagram of a synchronous machine, we can see a voltage
    * (E^af) induce voltage in generator
    * (Xs) synchronous reactance
    * (Ra) armature resistance and
    * (V) applied voltage
    * (Ia) armature current
    by simply applying the ohm law V^a=−RaIa−jXsIa+Eaf ==> (E^af - V^a) = RaI^a - jXsI^a
    this looks a little bit as the formula S=P+jQ, with Q being a reactance, if we multiply both sides by I with I=I^a in series
    I*(E^af - V^a) = I*(RaI^a - jXsI^a)
    we know S=E*I so S = RaI^2-jXsI^2
    we see that it will depend on the applied voltage and Internal resistance. Now, the total internal resistance will vary depending on the configuration Y or D.
    I would go with the applied voltage, i mean that's how i try to understand that.

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    Quote Originally Posted by joeldjiogo View Post
    considering the internal diagram of a synchronous machine, we can see a voltage
    * (E^af) induce voltage in generator
    * (Xs) synchronous reactance
    * (Ra) armature resistance and
    * (V) applied voltage
    * (Ia) armature current
    by simply applying the ohm law V^a=−RaIa−jXsIa+Eaf ==> (E^af - V^a) = RaI^a - jXsI^a
    this looks a little bit as the formula S=P+jQ, with Q being a reactance, if we multiply both sides by I with I=I^a in series
    I*(E^af - V^a) = I*(RaI^a - jXsI^a)
    we know S=E*I so S = RaI^2-jXsI^2
    we see that it will depend on the applied voltage and Internal resistance. Now, the total internal resistance will vary depending on the configuration Y or D.
    I would go with the applied voltage, i mean that's how i try to understand that.

    I think that you are mixing up cause and effect. Current will vary, not the reactance.

    Saturation is the right answer. Cores are simulated using variable inductances to model saturation.

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