What is the difference between 277 volts and 120.?
Answer:
The literal difference is 157 volts, not 57.
In the USA, the most common 3-phase utilization voltage is 480 volts line-to-line. In a 480 volt 3-phase power distribution system derived from a wye secondary winding of a transformer, the line to neutral voltage is 277 volts. Three single phase 277 volt connections are available in that kind of system, but I am not aware of any significant usage of the single phase connections. Single phase transformers may be connected to step the 277 volts down to 120 volts or the US standard for single phase usage, 240 volts with two 120 volt connections and a neutral.
57 Volts
The obvious difference is 57 volts, but I know that's not what your after.
Some years ago, the cities, county buildings, state buildings and other government building had the standard 115 to 120 volt power, and all of their fans and electrical equipment was for this standard voltage, well, needless to say, many of these employees had all of the new fans and whatever they needed, for free, at the taxpayers expense, and it was then that most government buildings went to the 277 power, which was not available to the average homeowner. Theft stopped quick. Another trick they applied was to convert many of their systems to DC current, which again stopped a lot of theft, not all, but a lot.
120V is line-neutral on a single-phase 120/240 system, like most homes. 277V is line-neutral on a 480/277 three-phase system, often used in industrial settings.
if a building like to economize in the transformer to be installed in their building, then they will specify a 480 volts wye secondary with a neutral of 277 volts that will be used for their lighting needs. here in canada, we are using 277 volts ballasts for our high bay mercury lighting and those double fluorescent lighting from 4 footer to 8 footer, 480 volts for motor loads, so the transfor mer for 110 v convenience outlets for offices became smaller in kva rating
277v is the line to neutral voltage on a 480v, 3 phase system. 120v is the common domestic voltage, although this is usually one leg of a 240v secondary that has a centre tap neutral. 120v is also the line to neutral voltage of a 208v, 3 phase system. 120v is also the voltage often used in industry for controls.
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