When the line-to-line voltage at the service equipment drops to 456 volts for a 277/480-volt 3Ø, 4W service, what is the actual line-to-neutral voltage available?

To determine the line-to-neutral voltage when the line-to-line voltage drops to 456 volts in a 277/480-volt three-phase, four-wire service, we can use the relationship between line-to-line and line-to-neutral voltages.

In a three-phase system, the line-to-neutral voltage is calculated from the line-to-line voltage with the formula:

Line-to-Neutral Voltage = Line-to-Line Voltage / √3

Substituting the given line-to-line voltage of 456 volts into the formula:

Line-to-Neutral Voltage = 456 volts / √3

≈ 456 volts / 1.732

≈ 263 volts

This calculation shows that when the line-to-line voltage is 456 volts, the corresponding line-to-neutral voltage will be approximately 263 volts. Thus, the correct answer is the first option, which reflects this calculation properly.

Understanding this relationship is crucial, as it allows electrical professionals to effectively assess voltage levels and ensure equipment operates under the appropriate conditions, keeping in mind that under load or due to other factors, actual voltages can fluctuate.