Question

A 3-phase, 7 kVA, 400 V, 2-pole, star-connected synchronous machine has negligible armature resistance and Xs-60/phase at rated terminal voltage The machine first runs as a generator in parallel with 3-phase, 400 V, 50 Hz power supply 111 Determine the generated voltage and torque angle of the machine operating as a generator, delivering rated kVA at 0 9 pf lagging Draw and label the corresponding phasor diagram for this condition 1 12 If the field excitation is increased by 18% (without changing the mechanical input power), find the new armature current and pf 12 With the original field current (as in Q1 1), the mechanical input power is slowly increased Under conditions of maximum power transfer find the corresponding power, armature current and pf 1 3

Answer 1

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2 lead