In three-phase systems, what are the standard connection configurations called?

• A. Delta and Wye
• B. Ring and Star
• C. Series and Parallel
• D. Open and Closed

Answer: (A)

Connecting three-phase windings can be done mainly in two standard ways: Delta and Wye. In a delta, the windings form a closed triangle and each line conductor connects to a corner; there is no neutral. This arrangement makes the line voltage equal the winding (phase) voltage, and the line current is √3 times the phase current due to vector addition of the phase currents. In a wye configuration, one end of each winding is tied together at a neutral point and the other ends connect to the three lines; a neutral is available for line-to-neutral loads. Here the line voltage is √3 times the phase voltage, while the line current equals the winding current. These relationships explain why these two configurations are the standard choices in three-phase systems.