A three-phase four-wire system is referred to as a:

• A. Delta
• B. Wye
• C. Open delta
• D. Balanced delta

Answer: (B)

A three-phase system with a neutral conductor is a Wye (star) configuration. In this setup, the three phase windings share a common connection point, creating a neutral that can carry unbalanced currents and provide line-to-neutral voltages for lighting and control circuits. The line-to-neutral voltage is the phase voltage, and it relates to the line-to-line voltage by V_LL = √3 × V_LN.

Why the others don’t fit: a Delta configuration connects the three windings in a triangle and traditionally has no neutral, so there isn’t a fourth conductor for a neutral. Open delta is a three-transformer arrangement lacking one transformer, which also does not provide a standard neutral. Balanced delta refers to a delta with balanced loads but still no neutral. The presence of a neutral (four wires total) is the hallmark of the Wye arrangement.