The feeder originates from a 120/240-volt, 3Ø, 4-W switchboard or panelboard. This description describes the feeder as being what type of supply?

The feeder originates from a 120/240-volt, 3Ø, 4-W switchboard or panelboard. This description describes the feeder as being what type of supply?

• A. 120/240-volt, three-phase, four-wire
• B. 120/208-volt, three-phase, four-wire
• C. 240/480-volt, three-phase, four-wire
• D. 120/240-volt, single-phase, four-wire

Answer: (A)

Line-to-neutral and line-to-line voltages tell you what kind of three-phase, four-wire system you’re dealing with. If a feeder is described as 120/240-volt, three-phase, four-wire, that means each hot leg to neutral provides 120 volts, and any two hot legs to each other provide 240 volts, with a neutral conductor present (the four wires: three hots plus neutral). This is the classic 120/240-volt three-phase, four-wire setup, often a center-tapped delta arrangement that yields 120 V to neutral and 240 V between lines. That’s why the correct description is 120/240-volt, three-phase, four-wire. The other options would imply different line-to-line voltages or a single-phase system, which doesn’t match the given description.

Line-to-neutral and line-to-line voltages tell you what kind of three-phase, four-wire system you’re dealing with. If a feeder is described as 120/240-volt, three-phase, four-wire, that means each hot leg to neutral provides 120 volts, and any two hot legs to each other provide 240 volts, with a neutral conductor present (the four wires: three hots plus neutral). This is the classic 120/240-volt three-phase, four-wire setup, often a center-tapped delta arrangement that yields 120 V to neutral and 240 V between lines.

That’s why the correct description is 120/240-volt, three-phase, four-wire. The other options would imply different line-to-line voltages or a single-phase system, which doesn’t match the given description.