Q.1 Max. Marks: 20 A three-phase, 400V, 10kVA star-connected cylindrical synchronous [6] machine is synchronized with an infinite bus bar at rated voltage. The synchronous reactance is $X_s$=7 ? per phase. The alternator is driven by a 220V, 10kW DC shunt motor. Neglect all losses. Determine (a) The excitation voltage and the load angle of the alternator when it delivers rated kVA at unity power factor (b) With the driving torque of DC shunt motor unaltered, the excitation voltage is increased by 25%. Find the new load angle, current and power factor. Also obtain the maximum stable power output of the alternator and the corresponding values of current and pf.
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