A 3 phase, 208V, 4 pole, 60Hz, Y connected synchronous generator has a synchronous reactance of 8 ohm. Assume the resistance of this generator is negligible. The machine terminal voltage is maintained constant at 208V (line to line).
i) Find the synchronous speed in rpm as well as in radians/sec.
ii) The machine is delivering a total of 3 kVA at 0.8 power factor lagging. Determine the excitation voltage (Eaf) and the load angle (?) for this condition. Also draw the phasor diagram
iii) What is the maximum power that machine can be supply in case ii)
iv) If the filed current (If) is increased by 20% ( with constant mechanical input power corresponding to case ii) , find new excitation voltage, new load angle, the new stator current, new power factor and the reactive power kVAR supplied by the machine.
v) For case iv, find the new maximum power the machine can supply.
vi) Draw P vs f diagrams for case ii) and case iv). Show the load angles corresponds to the 3 KVA , 0.8 pf load.
vii) In case ii), for the same real power delivered what should be the new excitation voltage to get a power factor of 0.8 lead.