In a three-wire Y-connected generator with phase (line-to-neutral) voltages of 2 kV, determine the magnitude of each line-to-line voltage.
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A2,000 V
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B6,000 V
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C666 V
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D3,464 V
Answer
Correct Answer: 3,464 V
Explanation
Introduction / Context:Calculating line-to-line voltage from a known phase voltage in a Y connection is a frequent task in power distribution and equipment specification. The √3 factor is a direct consequence of 120° phasor geometry in balanced three-phase systems.
Given Data / Assumptions:
- Y-connected generator (balanced).
- Phase voltage V_phase = 2 kV (rms, line-to-neutral).
- Find V_line (rms, line-to-line).
Concept / Approach:For Y: V_line = √3 * V_phase. The line-to-line voltage is the phasor difference of two line-to-neutral voltages separated by 120°, yielding a magnitude √3 times larger than a single phase voltage.
Step-by-Step Solution:
Use the relation V_line = √3 * V_phase.Compute: √3 * 2,000 ≈ 1.732 * 2000 = 3,464 V.Verification / Alternative check:Common standards (e.g., 230/400 V) follow the same ratio. This consistency reinforces the calculation method and result here.
Why Other Options Are Wrong:
- 2,000 V: This would be true for Δ (line = phase), not for Y.
- 6,000 V: Assumes a factor of 3 rather than √3.
- 666 V: An inverse-type confusion (phase vs line) and off by a large factor.
Common Pitfalls:
- Mixing Δ and Y relationships or forgetting the 120° vector geometry.
Final Answer:3,464 V