Previous Year Question

Correct Answer

B — Changing the excitation

Concept and Reasoning

For a synchronous generator connected to a strong bus, real power is controlled mainly by mechanical input, while reactive power is controlled mainly by field excitation. Increasing field current raises internal emf and generally increases reactive-power export. Hence option B.

Calculation / Key Relation

Q control ↔ excitation/field current

P control ↔ prime-mover input

Exam Takeaway

Generator excitation is the primary reactive-power control.

Common Mistake

Do not use governor/mechanical input as the main reactive-power control variable.