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A synchronous generator is running over excited with a Ef=1.40pu. This machine, with a synchronous reactance of 1.2pu, is delivering a synchronous power of 0.5pu to the bus. If the prime-mover torque is increased by 1%, by how much will the reactive power, Q change?(a) -0.475 %(b) 0.475%(c) 4.75%(d) -4.75%I got this question at a job interview.I'd like to ask this question from Power Angle Characteristics of Synchronous Machines in chapter Synchronous Machines of Electrical Machines

Answer» RIGHT OPTION is (a) -0.475 %

For EXPLANATION I WOULD SAY: dQ/dδ = -EVsinδ/X

dP/dδ = EVcosδ/X

dQ/dP = -tanδ = -tan25.4 = -0.475

dQ = -0.475%.


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