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Lighting and general purpose receptacles are at 120 volts AC, with larger devices fed by three wire single-phase circuits at 240 volts. In commercial construction, three-phase circuits are often used. Common 3 phase configurations within a building are 208v/120 wye, 120/240 center tapped delta and 480v/277v wye. Lighting is usually fed by 277 V ...
So if A–B, B–C and C–A are all 240 volts, then A–N and C–N will both be 120 volts, but B–N will be 208 volts. Other types of three-phase supplies are wye connections, ungrounded delta connections, or corner-grounded delta [2] (ghost leg configuration) connections. These connections do not supply split single-phase power, and do not ...
120/208-volt wye and 240-volt delta Colour Use ... White: Neutral (grounded conductor) Black: Ø 1 Red: Ø 2 Blue: Ø 3 277/480-volt wye or 480-volt delta Colour Use
This setup produces three different voltages: If the voltage between the center tap (neutral) and each of the top and bottom taps (phase and anti-phase) is 120 V (100%), the voltage across the phase and anti-phase lines is 240 V (200%), and the neutral to "high leg" voltage is ≈ 208 V (173%). [21]
120/208/240 V service 277/480 V service 347/600 V service 240/415 V service Voltage Grounded Voltage Grounded Voltage Grounded Voltage Grounded no yes no yes no yes no yes hot–neutral 120 V: 1; ML1: 5; TT; SS1; ML2. 277 V: 3: 7: 347 V-24: 240 V-25 hot–hot 240 V (split-phase) 208 V (wye) 2: 6: 480 V-8: 600 V: 4: 9: 415 V-- hot–hot ...
120 V 120 V 240 V 240 V 120/208 V 277/480 V 120/240 V 240 V 480 V 60 Hz NEMA 5-20R outlets, which are similar to type B but have a T-shaped neutral slot, are sometimes used for higher current 120 V equipment (up to 20 A). U.S. Virgin Islands: A B NEMA 1-15P NEMA 5-15P 110 V 190 V 60 Hz Uruguay: C, F, I, L 230 V 400 V 50 Hz
The controlling relay monitors voltage and current in the transformer, and opens or closes the contact mechanism through electrical signals. The relay uses a power/time curve so that small, short term reverse power flow (such as from elevator hoists) are ignored. Spot units will be 277/480 and the grid units will be 120/208.
These two give different voltages from a given supply. For example, on a 120/208 three-phase system, which is common in North America, the phase-to-neutral voltage is 120 volts and the phase-to-phase voltage is 208 volts. This allows single-phase lighting to be connected phase-to-neutral.