-
In a 3-phase Δ/ Y transformer shown in the figure, the phase displacement of secondary line voltages with corresponding primary line voltages will be
-
- zero
- 30° lag
- 30° lead
- 180°
Correct Option: B
Consider any pair of line terminals on primary and secondary sides.
Consider pair AB.
Let VA1B1 be reference on primary side
VA1B1 = V ∠0°
VB1C1 = V ∠– 120°
VC1A1 = V ∠120°
VA2n = k VA1C1 = − k VC1A1 = − k ∠120°
VnB2 = k VA1B1 = k V ∠0°
VA2B2 = VA2n − VnB2 = k V( ∠−60° + ∠0°)
= √3 kV ∠−30°
Thus line voltage VA2B2 on secondary side which equals √3 kV ∠−30°, lags corres-ponding line voltage VA1B1 on primary side, which is V ∠0°; by 30°.
