Commercial North American Voltage Ratings: 120/208/277/480V

North America’s commercial power distribution mainly adopts two types of three-phase four-wire wye systems, following the formula:Line Voltage = Phase Voltage × 1.732. A 120 V phase voltage corresponds to a 208 V line voltage, while a 277 V phase voltage matches a 480 V line voltage. These four voltage ratings derive from the two systems instead of separate power grids.
The 208Y/120V system is widely used in small stores and offices: 120V supplies wall outlets and office appliances, and 208V powers three-phase equipment such as air conditioners and kitchen machinery. The 480Y/277V system serves as the main power supply for shopping malls andfactories. 277V is dedicated to commercial lighting, and 480V drives heavy-load motors and water pumps; higher distribution voltages cut downcable power loss. There is also an older 120/240 high-leg delta system, whose high leg measures roughly 208V to neutral. It is easily confused with the wye-type 208V system and cannot share wiring schemes.
The 120V residential standard has been used for over a century, lowering electric shock risks yet consuming more copper materials. Communities install transformers on demand: residential areas only get 120/240V, while commercial buildings are equipped with matching three-phase systems.Equipment selection cannot rely solely on voltage ratings; the wye/delta configuration and power tapping mode must be distinguished. For industrial machinery under the 480V system, control circuits mostly adopt 120V AC or 24V DC rather than 277V.