In a synchronous machine, ‘V’ curves present the variation of
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Answer & Explanation
Correct AnswerA. Armature current with excitation (field) current
Quick Explanation
A synchronous-machine V-curve plots armature current against field current at constant mechanical load and terminal voltage. As excitation changes from under- to over-excited, armature current falls to a minimum near unity power factor and rises again, giving the V shape. Hence option A.
Formula / Key Relation
V-curve: Ia versus If at constant load
Detailed Explanation
Correct Answer
A — Armature current with excitation (field) current
Concept and Reasoning
A synchronous-machine V-curve plots armature current against field current at constant mechanical load and terminal voltage. As excitation changes from under- to over-excited, armature current falls to a minimum near unity power factor and rises again, giving the V shape. Hence option A.
Calculation / Key Relation
V-curve: Ia versus If at constant load
Exam Takeaway
V-curve minimum approximately corresponds to unity power factor.
Common Mistake
Do not confuse a V-curve with an inverted V-curve, which plots power factor versus field current.
Quick Trick
V-curve minimum approximately corresponds to unity power factor.
Common Mistake
Do not confuse a V-curve with an inverted V-curve, which plots power factor versus field current.
Exam Tip
V-curve minimum approximately corresponds to unity power factor.
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