In a star-delta transformer, the delta side phase voltage leads the star sides phase voltage by an angle

(a)  + 30°.
(b)  + 45°.
(c)  – 30°.
(d)  – 45°.

Answer
 (a)  + 30°.

Explanation:
  • In a star-delta transformer, the delta side phase voltage leads the star sides phase voltage by an angle + 30°.
  • The phase shift is the angular displacement between the maximum positive value of the alternating quantities having the same frequency. 
  • In other words, the angular displacement between high voltage and the low voltage terminal and the corresponding neutral points (real or imaginary), expressed with reference to high voltage side is known as phase displacement (or shift) of the transformer.

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