In a three-phase system, what voltage is measured between secondaries?

In a three-phase system, what voltage is measured between secondaries?

• A. 208 volts
• B. 120 volts
• C. 277 volts
• D. 69 kV

Answer: (A)

In a 120/208 V three-phase system arranged in a wye, each phase to neutral is 120 V, and the voltage between any two phases (between two secondaries) is the line‑to‑line value. The line-to-line voltage in a wye system is the phase voltage multiplied by the square root of 3: V_LL = √3 × 120 V ≈ 208 V. So measuring between two secondaries yields about 208 V. The 120 V value would be from a single secondary to neutral, not between secondaries. The 277 V value is the line-to-neutral voltage for a 480Y/277 V system (not applicable here), and 69 kV is a high transmission voltage, not a typical secondary in this context.

In a 120/208 V three-phase system arranged in a wye, each phase to neutral is 120 V, and the voltage between any two phases (between two secondaries) is the line‑to‑line value. The line-to-line voltage in a wye system is the phase voltage multiplied by the square root of 3: V_LL = √3 × 120 V ≈ 208 V. So measuring between two secondaries yields about 208 V.

The 120 V value would be from a single secondary to neutral, not between secondaries. The 277 V value is the line-to-neutral voltage for a 480Y/277 V system (not applicable here), and 69 kV is a high transmission voltage, not a typical secondary in this context.