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Three identical star connected resist or s of 1.0 pu are connected to an unbalanced 3 phase supply. The load neutral is isolated. The symmetrical components of the line voltages in pu are:
Vab1 = X ∠1, Vab2 = Y∠2.
If all the pu calculations are with the respective base values, the phase to neutr al sequence voltages are
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- Van1 = X ∠ (θ1 + 30°),
Van2 = Y ∠(θ2 – 30°) - Van1 = X ∠ (θ1– 30°),
Van2 = Y ∠(θ2 + 30°) - Van1 = 1/√3 X ∠ (θ1 – 30°), Van2 = 1/√3 Y∠(θ2 – 30°)
- Van1 = 1/√3 X ∠ (θ1 – 60°),
Van2 = 1/√3 Y ∠(θ2 – 60°)
- Van1 = X ∠ (θ1 + 30°),
Correct Option: C
Assuming Va as reference phasor,
Van1 = V∠0°
Vbn1 = V∠– 120°
Vab1 = Van1 - Vbn1
= V∠0° – V∠– 120°
= √3Van1 ∠30°
Given, Vab1 = X ∠θ2
Then, Y ∠θ2 = √3 Van2 ∠ - 30°
⇒ Van2 = Y√3 ∠θ2 + 30°