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Electric Machinery Fundamentals (Solutions Manual) Part 6

Tham khảo tài liệu 'electric machinery fundamentals (solutions manual) part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Also the synchronous reactance will be reduced by a factor of 5 6. v 5 0.9 0.7 X 6 c At 50 Hz rated conditions the armature current would be 1 T - 0 M A 524 A 3 3 11.0 kV A L The power factor is 0.8 lagging so IA 5247 36. . The phase voltage is 11.0 kV V. Therefore the internal generated voltage is A 3 6351 e VI I A A S R jX Ea 6351 0 j 0 75 5247 o 36.87 a Ea 9264 19.9 V The resulting voltage regulation is 9264 6351 . . . . V ------100 45.9 6351 Because voltage apparent power and synchronous reactance all scale linearly with frequency the voltage regulation at 50 Hz is the same as that at 60 Hz. Note that this is not quite true if the armature resistance Ra is included since RA does not scale with frequency in the same fashion as the other terms. 5-24. Two identical 600-kVA 480-V synchronous generators are connected in parallel to supply a load. The prime movers of the two generators happen to have different speed droop characteristics. When the field currents of the two generators are equal one delivers 400 A at 0.9 PF lagging while the other delivers 300 A at 0.72 PF lagging. a What are the real power and the reactive power supplied by each generator to the load b What is the overall power factor of the load c In what direction must the field current on each generator be adjusted in order for them to operate at the same power factor Solution a The real and reactive powers are T aT V s c o P 3 480 V 400 A 0.9 299 kW aT T 1 Q s 1 3 480 V 400 A sin cos 0.9 145 kVAR aT aT V 1 co P 3 480 V 200 A 0.72 120 kW aT D1 2 Q sV Ị 3 480 V 200 A sin cos 0.72 115 kVAR b The overall power factor can be found from the total real and reactive power supplied to the load. TOT 1 P P 2P 9 kW 120 kW 419 kW TOT 1 Q Q 1Q 5 kVAR 115 kVAR 260 kVAR The overall power factor is 141 PF cos tan 1 -TQ D - 0.850 lagging Tp T c The field current of generator 1 should be increased and the field current of generator 2 should be simultaneously decreased. 5-25. A generating station for a power system .