Difficulty: Medium
Correct Answer: each phase voltage equals the difference of the corresponding load voltages
Explanation:
Introduction / Context:
Mixed Δ–Y connections are common in transformers and generator–load interfaces. Understanding how source phase voltages map to load terminal voltages avoids confusion when converting between line-to-line and line-to-neutral measures and when drawing phasor diagrams for interconnections.
Given Data / Assumptions:
Concept / Approach:
In Δ, each phase element is across a pair of lines; thus the source phase voltage is a line-to-line voltage (difference of two line phasors). The Y load phase voltage is a line-to-neutral voltage. Because line-to-line voltages are differences of line-to-neutral voltages, one can say each Δ phase voltage equals the vector difference of two corresponding Y load (line-to-neutral) voltages.
Step-by-Step Reasoning:
Verification / Alternative check:
Draw the phasor diagram: V_an, V_bn, V_cn are 120° apart. The vector subtraction V_an − V_bn produces the familiar line-to-line magnitude √3 times the phase magnitude, aligning with Δ phase values.
Why Other Options Are Wrong:
Common Pitfalls:
Final Answer:
each phase voltage equals the difference of the corresponding load voltages
Discussion & Comments