What is the configuration if the secondary voltage is 277/480?

The configuration of a secondary voltage described as 277/480 volts indicates a wye (Y) connection. In this type of system, the line voltage (the voltage between any two of the three lines) is represented by 480 volts, while the phase voltage (the voltage between any one line and the neutral) is represented by 277 volts.

In a wye connection, the phase voltage can be determined by dividing the line voltage by the square root of three (approximately 1.732). Thus, to find the phase voltage from the line voltage in a three-phase system, you would have:

Phase Voltage = Line Voltage / √3

Phase Voltage = 480 volts / √3 ≈ 277 volts

This calculation aligns with the voltages given in the question, confirming that a wye configuration is being described.

On the other hand, a delta configuration would yield a different voltage relationship, where the line voltage and phase voltage are equal, leading to values that do not correspond to 277/480 volts. Series and single-phase configurations are not applicable in this context as they do not support a three-phase system characteristic of the voltages given, further confirming that the appropriate configuration here is a wye connection.