A 120/240-volt, 1Ø, 3-wire system is commonly known as what?

A 120/240-volt, 1Ø, 3-wire system is commonly known as what?

• A. Split-phase system
• B. Three-phase wye
• C. Three-phase delta
• D. Open delta system

Answer: (A)

This is a split-phase distribution: a center-tapped transformer provides two hot legs that are opposite in phase. Each leg delivers 120 V to neutral, and the two legs are 180 degrees apart, giving 240 V between them. That setup uses three wires—two hot conductors plus a neutral—and is the standard residential 120/240-V single-phase service in many parts of the world. The other options describe different electrical systems: three-phase wye gives three hot lines (often with a neutral) and different line-to-neutral or line-to-line voltages; three-phase delta is a three-hot configuration with its own voltage relationships and may or may not include a neutral; open delta is a non-closed delta arrangement used for specialized cases. None of these match the typical 120/240-V, single-phase, three-wire residential service.

This is a split-phase distribution: a center-tapped transformer provides two hot legs that are opposite in phase. Each leg delivers 120 V to neutral, and the two legs are 180 degrees apart, giving 240 V between them. That setup uses three wires—two hot conductors plus a neutral—and is the standard residential 120/240-V single-phase service in many parts of the world.

The other options describe different electrical systems: three-phase wye gives three hot lines (often with a neutral) and different line-to-neutral or line-to-line voltages; three-phase delta is a three-hot configuration with its own voltage relationships and may or may not include a neutral; open delta is a non-closed delta arrangement used for specialized cases. None of these match the typical 120/240-V, single-phase, three-wire residential service.