When a 3Ø, 4-W supply system delivers 277/480 volts, how is the system connected?

A 3-phase, 4-wire supply system that delivers voltages of 277/480 volts is typically connected in a wye configuration. In this kind of system, the line voltage (480 volts) is the voltage measured between any two of the three phases, while the phase voltage (277 volts) is the voltage measured from any one phase to the neutral point.

In a wye connection, each phase of the supply is connected to a common neutral point, resulting in a lower phase voltage which is derived from the line voltage divided by the square root of three. This is significant for systems providing power to three-phase loads, as it allows for the use of both three-phase and single-phase loads efficiently.

Paralleled connections are not typically associated with standard transformations of voltages in three-phase systems. Delta connections, while common in three-phase wiring, would not result in the specific 277/480 volt output; rather, their coupling generates line voltages equal to phase voltages. Series connections do not apply in the context of three-phase systems for power distribution, as they are utilized in different applications like series circuits or certain types of load arrangements.

Thus, the wye connection is indeed the correct answer for a system providing