In a Wye (Y) configuration, how are line voltage and phase voltage related, and how are line current and phase current related?

• A. Vline = √3 × Vphase; Iline = Iphase
• B. Vline = Vphase; Iline = √3 × Iphase
• C. Vline = 3 × Vphase; Iline = Iphase
• D. Vline = Vphase/√3; Iline = √3 × Iphase

Answer: (A)

In a Wye (Y) configuration, each phase winding is connected from a line to neutral, so the phase voltage is the voltage across a single winding (line-to-neutral), while the line voltage is the voltage between two lines (line-to-line). The three phase voltages are 120 degrees apart, and when you take the difference between two line voltages, the resulting line-to-line voltage has a magnitude of √3 times the phase voltage. That’s why Vline = √3 × Vphase.

For current, the line current is the current flowing in the conductor from the source to the load for that phase, which is the same as the current through the corresponding phase winding. So Iline = Iphase.

Thus, in a Wye configuration, line voltage is √3 times the phase voltage, while line current equals the phase current.