Three identical cylindrical rotor generators, each rated 70MVA, 15 kV are connected to an infinite bus...

  

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Three identical cylindrical rotor generators, each rated 70MVA, 15 kV are connected to an infinite bus of 15kV. between the internal voltage of each machine and the infinit bus is 2 ohm/phase. The three machines are equally sharing a total load of 120 MW at 15kV, 0.8 lagging power factor. The reactance (a) Find the internal excitation emf of the syncronous machines when they are equally excited. 14 marks] (b) If the excitation emf of one of the machines is decreased by 20%, find the percentage change in the excitation voltage of the other two machines. Assume that the governor setting for all machine to remain unchanged. [3 marks) (e) In general, skitch the capability curve of a synchmous machine showing the four limits. [1 mark] Three identical cylindrical rotor generators, each rated 70MVA, 15 kV are connected to an infinite bus of 15kV. between the internal voltage of each machine and the infinit bus is 2 ohm/phase. The three machines are equally sharing a total load of 120 MW at 15kV, 0.8 lagging power factor. The reactance (a) Find the internal excitation emf of the syncronous machines when they are equally excited. 14 marks] (b) If the excitation emf of one of the machines is decreased by 20%, find the percentage change in the excitation voltage of the other two machines. Assume that the governor setting for all machine to remain unchanged. [3 marks) (e) In general, skitch the capability curve of a synchmous machine showing the four limits. [1 mark]

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a We are given 3 synchronous generator machines rated 70 kVA each Internal voltage of each machine i... View the full answer