In a triple phase system, metering from the neutral to a phase, how many volts should there be?

In a triple phase system, metering from the neutral to a phase, how many volts should there be?

• A. 120 volts
• B. 208 volts
• C. 240 volts
• D. 277 volts

Answer: (A)

In a three-phase wye system with a neutral, the voltage from neutral to any one phase is the phase-to-neutral voltage. In the common 120/208 V arrangement, that phase voltage is 120 V, while the voltage between any two phases (line-to-line) is about 208 V because V_LL = √3 × V_LN (√3 × 120 ≈ 208). So metering from neutral to a single phase should read 120 V in this typical setup. (If the system were 277/480 V, neutral-to-phase would read 277 V instead.)

In a three-phase wye system with a neutral, the voltage from neutral to any one phase is the phase-to-neutral voltage. In the common 120/208 V arrangement, that phase voltage is 120 V, while the voltage between any two phases (line-to-line) is about 208 V because V_LL = √3 × V_LN (√3 × 120 ≈ 208). So metering from neutral to a single phase should read 120 V in this typical setup. (If the system were 277/480 V, neutral-to-phase would read 277 V instead.)