What is the voltage across each winding of a wye-connected transformer secondary that has a line-to-line voltage of 480 volts?

In a wye-connected transformer configuration, the relationship between the line-to-line voltage and the line-to-neutral (or phase) voltage is a key concept. The line-to-line voltage is the voltage measured between any two of the three phases, while the line-to-neutral voltage is the voltage measured from any phase to the neutral point.

To find the voltage across each winding (the line-to-neutral voltage) when the line-to-line voltage is known, the formula to use is:

[ V_{phase} = \frac{V_{line-to-line}}{\sqrt{3}} ]

Given that the line-to-line voltage is 480 volts, the calculation for the line-to-neutral voltage becomes:

[ V_{phase} = \frac{480}{\sqrt{3}} \approx \frac{480}{1.732} \approx 277.1 , \text{volts} ]

This value approximates to 277 volts, which corresponds to the voltage across each winding of the wye-connected transformer secondary. Thus, this is the correct choice based on the principles of three-phase power systems. Understanding this relationship allows electrical professionals to analyze and design systems correctly, ensuring the correct application of voltage levels.