The equivalent circuit of synchronous generator in show in fig.(a) .it is redrawn in fig (b) by taking Xs = XAR + Xa

**Lagging Power Factor cos**Î¦ :

Fig shows the phasor diagram for lagging load. the power factor is cosÎ¦ lagging. In this diagram the terminal voltage V is taken as reference phasor along

*OA*such that*OA*= V. For lagging power factor cos Î¦ the direction of the armature current Ia lags behind V by angle f along*OB*, where*OB*= Ia. the voltage drop in the armature resistance is Ia Ra . It is represented by phasor*AC*.**Ia Xs**. ti is represented by

*CD*. it leads the current Ia by 90 and , therefore

*CD*drawn in a direction perpendicular to OB the total voltage drop in the synchronous impedance is the phasor sum Ia Ra and

**Ia Xs**. ti is represented by

*AD*. the phasor

*OD*represents Ea.

**Unity Power Factor :**

The phasor diagram for unity power factor is shown in figure.

**Leading Power Factor cos**Î¦ :

The phasor diagram for leading power factor is shown in figure.

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