AExE01 · Chapter 1Basic Electrical & Electronics🏛️ Past Licensure QuestionID: 13d45bd9

In a balanced three-phase star-connected system, what is the relationship between line voltage ( $V_L$ ) and phase voltage ( $V_{ph}$ )?

Multiple Choice Options

A
Line voltage is equal to phase voltage
B
Line voltage is the product of phase voltage and
$\sqrt{3}$
✓ Correct Option
C
Phase voltage is the product of line voltage and
$\sqrt{3}$
D
None of the above

Detailed Technical Solution & Explanation

In a balanced 3-phase star (Wye) connection, line voltage ( $V_L$ ) is measured between any two line conductors. Since each line voltage is the phasor difference of two phase voltages separated by 120°, its magnitude is: $V_L = 2 V_{ph} \cos(30°) = \sqrt{3} V_{ph} \approx 1.732 V_{ph}$ .

Option Analysis:

•

Option A (Line voltage is equal to phase voltage): Incorrect.

V_L = V_{ph}

holds in a delta (

\Delta

) connection, not a star connection.

•

Option B (Line voltage is the product of phase ...): Correct. In star connection,

V_L = \sqrt{3} V_{ph}

•

Option C (Incorrect. Phase voltage is smaller):

V_{ph} = V_L / \sqrt{3}

•

Option D (None of the above): Incorrect.

Reference: Demo2 · Set 2NEC Licensure Syllabus

In a balanced three-phase star-connected system, what is the relationship between line voltage ( $V_L$ ) and phase voltage ( $V_{ph}$ )?

Multiple Choice Options

Detailed Technical Solution & Explanation

Option Analysis:

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In a balanced three-phase star-connected system, what is the relationship between line voltage ( $V_L$ ) and phase voltage ( $V_{ph}$ )?

Multiple Choice Options

Detailed Technical Solution & Explanation

Option Analysis:

Want to practice this topic interactively?