Which of the following is not a necessary condition for synchronizing an incoming alternator to an already operating alternator?
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Answer & Explanation
Correct AnswerD. Same prime mover speed
Quick Explanation
Before connecting an incoming alternator to live busbars, its terminal voltage magnitude, frequency and phase sequence must match the bus, and the phase angle must be near zero at closing. The condition identified in option D is not a necessary synchronizing condition.
Formula / Key Relation
Synchronize: equal V, equal f, same phase sequence, zero phase-angle difference at closing
Detailed Explanation
Correct Answer
D — Same prime mover speed
Concept and Reasoning
Before connecting an incoming alternator to live busbars, its terminal voltage magnitude, frequency and phase sequence must match the bus, and the phase angle must be near zero at closing. The condition identified in option D is not a necessary synchronizing condition.
Calculation / Key Relation
Synchronize: equal V, equal f, same phase sequence, zero phase-angle difference at closing
Exam Takeaway
Remember the four synchronizing checks: V, f, sequence, phase angle.
Common Mistake
Do not include an operating variable that is not part of the electrical synchronizing conditions.
Quick Trick
Remember the four synchronizing checks: V, f, sequence, phase angle.
Common Mistake
Do not include an operating variable that is not part of the electrical synchronizing conditions.
Exam Tip
Remember the four synchronizing checks: V, f, sequence, phase angle.
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