If the line-to-line voltage is 480 V, what is the approximate line-to-neutral voltage in a 480 V three-phase WYE system?

If the line-to-line voltage is 480 V, what is the approximate line-to-neutral voltage in a 480 V three-phase WYE system?

• A. 277 V
• B. 480 V
• C. 347 V
• D. 208 V

Answer: (A)

In a three-phase WYE system, the line-to-line voltage is √3 times the line-to-neutral (phase) voltage, so V_LL = √3 × V_LN. Therefore, V_LN = V_LL / √3. With a line-to-line voltage of 480 V, the line-to-neutral voltage is 480 / √3 ≈ 480 / 1.732 ≈ 277 V. So the approximate line-to-neutral voltage is 277 V. The other values don’t fit this relationship for a 480 V line-to-line system: 480 V would be the line-to-line value, not the neutral voltage; 347 V would correspond to a system with about 600 V line-to-line (600 / √3 ≈ 347 V); 208 V is typical for a 120/208 V three-phase system, not a 480 V one.

In a three-phase WYE system, the line-to-line voltage is √3 times the line-to-neutral (phase) voltage, so V_LL = √3 × V_LN. Therefore, V_LN = V_LL / √3. With a line-to-line voltage of 480 V, the line-to-neutral voltage is 480 / √3 ≈ 480 / 1.732 ≈ 277 V. So the approximate line-to-neutral voltage is 277 V.

The other values don’t fit this relationship for a 480 V line-to-line system: 480 V would be the line-to-line value, not the neutral voltage; 347 V would correspond to a system with about 600 V line-to-line (600 / √3 ≈ 347 V); 208 V is typical for a 120/208 V three-phase system, not a 480 V one.