To supply 480-volt, 3-phase power with transformer secondary coils banked in a wye configuration, what should the transformer secondary voltage ratings be?

In a wye configuration for transformers, the relationship between line voltage and phase voltage is critical to understand. In a three-phase system, the line voltage is equal to the phase voltage multiplied by the square root of three (approximately 1.732).

For a 480-volt line-to-line voltage in a wye configuration, the phase voltage can be calculated by dividing the line voltage by the square root of three. Therefore, to find the phase voltage (the voltage rating of each secondary coil), you would perform the following calculation:

[ \text{Phase Voltage} = \frac{\text{Line Voltage}}{\sqrt{3}} = \frac{480 \text{ volts}}{1.732} \approx 277.1 \text{ volts} ]

This calculation confirms that the appropriate transformer secondary voltage ratings for each winding in a wye configuration that supplies 480-volt, 3-phase power would be approximately 277 volts. This reflects the correct relationship in a three-phase wye system, making the answer accurate and necessary for proper transformer setup in such applications.