Q.3 A 10 KVA, three-phase, 8-pole, wye-connected 440V/50 Hz synchronous generator has negligible armature resistance and...

 

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Q.3 A 10 KVA, three-phase, 8-pole, wye-connected 440V/50 Hz synchronous generator has negligible armature resistance and a synchronous reactance of 20 per phase. If the generator is supplying 5 kVA to the grid at 0.8 lagging power factor, (a) Determine if the generator is over-excited or under-excited. (b) Determine the generator rotor speed. (2 marks) (1 marks) (c) Determine the per-phase excitation voltage magnitude and the power angle. (3 marks) (d) Draw the phasor diagram showing the terminal voltage, load current, voltage drop in the armature winding and excitation voltage. (3 marks) (e) If the field excitation is kept constant and the real power supplied to the grid is increased by 50%, what would be the new phase current supplied to the grid. (3 marks) Q.3 A 10 KVA, three-phase, 8-pole, wye-connected 440V/50 Hz synchronous generator has negligible armature resistance and a synchronous reactance of 20 per phase. If the generator is supplying 5 kVA to the grid at 0.8 lagging power factor, (a) Determine if the generator is over-excited or under-excited. (b) Determine the generator rotor speed. (2 marks) (1 marks) (c) Determine the per-phase excitation voltage magnitude and the power angle. (3 marks) (d) Draw the phasor diagram showing the terminal voltage, load current, voltage drop in the armature winding and excitation voltage. (3 marks) (e) If the field excitation is kept constant and the real power supplied to the grid is increased by 50%, what would be the new phase current supplied to the grid. (3 marks)