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30° Phase Shift

Which three-phase connection in a transformer will produce a phase-difference of 30° between its input and corresponding output line voltages?

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Answer & Explanation

Correct AnswerD. Star-delta

Quick Explanation

A 30° line-voltage phase displacement is produced when one side of a three-phase transformer is star-connected and the other is delta-connected. Star-star and delta-delta connections have zero nominal phase displacement. The connection in option D is therefore correct.

Formula / Key Relation

Y-Δ or Δ-Y → 30° phase displacement (sign depends on vector group)

Detailed Explanation

Correct Answer

D — Star-delta

Concept and Reasoning

Calculation / Key Relation

Y-Δ or Δ-Y → 30° phase displacement (sign depends on vector group)

Exam Takeaway

Star–delta family means 30° shift.

Common Mistake

Do not state the lead/lag direction without the actual vector-group clock notation.

Quick Trick

Star–delta family means 30° shift.

Common Mistake

Do not state the lead/lag direction without the actual vector-group clock notation.

Exam Tip

Star–delta family means 30° shift.

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Exam Path

Knowledge Path

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QP-112-202425.pdf2024Q. 154

30° Phase Shift

Quick Explanation

Formula / Key Relation

Detailed Explanation

Correct Answer

Concept and Reasoning

Calculation / Key Relation

Exam Takeaway

Common Mistake

Quick Trick

Common Mistake

Exam Tip

Previous Exam Appearances

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