The operating characteristics of a synchronous machine are seen under variable excitation and load condition. One of the parameter is kept constant while other is varied for studying these characteristics. The resistance of armature is neglected as it does not change the characteristics significantly. So the corresponding circuit is as shown in the Fig. 1.
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| Fig. 1 |
The phasor diagram corresponding to above condition is shown in the Fig. 2.
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| Fig. 2 |
Power Delivered to the infinite bus per phase is given by,
Pi = V . Ia cosΦ
From the above phasor diagram it can be seen that
From ∆OBC,
Substituting the above value of Ia cosΦ in the expression for power we get,
Note : The above power is the electrical power exchanged with bus bars. Angle δ between E and V is known as power angle.
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