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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

2. Originally Posted by kcorpuz
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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Originally Posted by kcorpuz
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.

4. Originally Posted by gchoquette
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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## Reactance of a synchronous machine

Originally Posted by kcorpuz
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=−RaIˆa−jXsIˆa+Eˆaf ==> (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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