A three-phase round-rotor synchronous generator, rated 16 kV and 200 MVA, has negligible losses and synchronous reactance of 1.65 per unit. It is operated on an infinite bus having a voltage of 15 kV. The internal emf Ei and the power angle S of the machine are found to be 24 kV (line to line) and 27.4°, respectively. (a) Determine the line current and the three-phase real and reactive power being delivered to the system. (b) If the mechanical power input and the field current of the generator are now changed so that the line current d the machine is reduced by 25% at the power factor of part (a), find the new internal cmf Ei and the power angle δ. (c) While delivering the reduced line current of part (b), the mechanical power input and the excitation are further adjusted so that the machine operates at unity power factor at its terminals. Calculate the new values of E; and δ.
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