What are the differences between delta and wye electrical power configurations, and where are each typically used in a building?

Delta and wye are two common configurations for three-phase electrical power distribution. In a delta configuration, the three phases are connected in a closed loop, resembling the Greek letter delta (Δ). There is no neutral connection in a standard delta configuration. The voltage between any two phases is the same, known as the line voltage. Delta configurations are often used for applications where high voltage is required, such as powering large motors or industrial equipment. A key characteristic is that if one phase is lost, the system can often continue to operate, albeit at reduced capacity. However, a standard delta configuration does not readily provide a single-phase voltage source. In a wye configuration, the three phases are connected to a common neutral point, resembling the letter Y. The voltage between any phase and the neutral point is known as the phase voltage, which is lower than the line voltage (the voltage between any two phases). Wye configurations are commonly used for general-purpose power distribution in buildings because they provide both three-phase and single-phase power. The single-phase voltage, derived from the phase-to-neutral connection, is suitable for lighting, receptacles, and small appliances. The three-phase voltage, derived from phase-to-phase connections, can power larger equipment like HVAC systems and pumps. In a building, a delta configuration might be used for the main power supply to large equipment, while a wye configuration is used for general power distribution throughout the building.