What is the line-to-line voltage of a 3Ø, 4-W supply system that delivers 277/480 volts?

In a 3-phase, 4-wire supply system, the voltage ratings provided often denote both the line-to-neutral (or phase-to-neutral) voltage and the line-to-line voltage. In this case, the specification of 277/480 volts indicates that 277 volts is the line-to-neutral voltage, while 480 volts is the line-to-line voltage.

To interpret this correctly, it's helpful to understand the relationship between the two types of voltage. For a 3-phase system, the line-to-line voltage can be calculated from the line-to-neutral voltage using the formula:

Line-to-line voltage = Line-to-neutral voltage × √3

In this instance, if you calculate from the noted line-to-neutral voltage of 277 volts, you'd find that:

Line-to-line voltage = 277 volts × √3 ≈ 480 volts

This supports the definition provided in the original question, where 480 volts is clearly stated as the line-to-line voltage. Therefore, the choice indicating 480 volts reflects the correct understanding of how voltages are designated in a 3-phase system. It captures the essential characteristics of the supply configuration and adheres to standard electrical terminology.