In a 480-volt 3-phase circuit connected to the delta primary of a 480 to 240-volt transformer, what is the voltage across any one primary winding?

In a 480-volt 3-phase circuit connected to the delta primary of a transformer, the voltage across any one primary winding corresponds directly to the line voltage, which in this scenario is 480 volts.

In a delta connection, each winding of the transformer sees the full line voltage across it. Thus, when dealing with a 3-phase system where the voltage is specified as 480 volts, that voltage is indeed the line-to-line voltage. Since the delta configuration means that the line voltage is equal to the voltage across each winding (phase), the voltage across any one primary winding remains at 480 volts.

This understanding is fundamental in electrical systems, particularly when analyzing transformer configurations and their relationship to line voltages in three-phase systems. The other options reflect voltages that do not apply to the primary winding in a delta configuration given the 480-volt line voltage scenario.