GATE 2014 EE (EE2) – Question 50
A synchronous generator with E_f = 1.3 pu and X_s = 1.1 pu supplies P = 0.6 pu to an infinite bus at 1.0 pu. Neglect stator resistance. Find reactive power Q delivered (pu).
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Correct answer: 0.10 to 0.12
Explanation
For a lossless cylindrical synchronous generator,P=EVsinδ/X. Hence sinδ=0.6×1.1/1.3=0.507692. On the usual stable low-angle branch,cosδ≈0.861538. Q=(EVcosδ−V²)/X=(√(1.3²−0.66²)−1)/1.1=**0.10907pu**. The positive sign indicates reactive power delivered to the bus.