Difficulty: Easy
Correct Answer: False
Explanation:
Introduction / Context:
Understanding the phasor relationships between phase and line quantities in Y (wye) systems is essential for measurements and design. The phase angle between line and phase voltages is a common exam point that tests phasor geometry, not just magnitudes.
Given Data / Assumptions:
Concept / Approach:
In a balanced Y system, line voltage leads its corresponding phase voltage by 30° (not 120°). Magnitude relationship: |V_line| = √3 * |V_phase|. Angle relationship: each line-to-line voltage is the vector difference of two phase voltages and is shifted by ±30° relative to a phase voltage.
Step-by-Step Solution:
Verification / Alternative check:
Draw the phasor diagram to visualize the 30° lead/lag and the √3 magnitude factor. Measurements on a balanced Y-connected alternator corroborate this geometry.
Why Other Options Are Wrong:
Conditions like unbalance or power factor do not change the inherent phase relation between instantaneous line and phase voltages in the source; the 30° relation is geometric.
Common Pitfalls:
Confusing the 120° separation between phase voltages with the line-to-phase angle. Remember: 120° is between phases; 30° is between a line voltage and its nearest phase voltage.
Final Answer:
False.
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