If a system is designated as delta or wye, the system is three-phase.

• A. three-phase
• B. single-phase
• C. either of these
• D. neither of these

Answer: (A)

Delta and wye describe how three windings are arranged in a three-phase system. Seeing those designations means there are three separate phase conductors delivering power, which is the defining feature of three-phase power. In a delta connection the windings form a closed triangle with three line conductors; in a wye connection the windings tie together at a neutral point and three line conductors provide the voltages. Because these arrangements are specific to three-phase systems, the correct conclusion is that the system is three-phase. A single-phase system uses only two conductors and is not described as delta or wye, so the other options don’t fit.