When a 3Ø, 4-W supply system delivers 120/240 volts, how is the system connected?

In a 3Ø, 4-W supply system delivering 120/240 volts, the system is typically connected in a Wye configuration. This configuration allows for two phase voltages: the line-to-line voltage is 240 volts, while the line-to-neutral (or phase) voltage is 120 volts, which is suitable for residential applications and standard lighting loads.

In a Wye connection, each of the three phases is connected to a common neutral point, which provides the ability to deliver both 120V and 240V as needed. This is essential for accommodating diverse electrical devices in residential settings that require different voltage levels.

Delta connections, while also used in three-phase systems, generally do not provide this kind of dual voltage output in the same manner as a Wye connection. Delta configurations connect each phase directly to each other without a neutral point, and typically only offer line-to-line voltages, which would not yield the 120-volt output directly. Thus, for a system that provides both 120 and 240 volts, the Wye connection is the correct choice.

Understanding the implications of these configurations helps in both installation and troubleshooting of electrical systems in various applications.