US 120VAC/240VAC question

600V is boderline high voltage in the US. Here in the UK and Europe we consider high voltage to be above 1kVAC.

Typical supplies are:

Single phase, 3 wire: 120/240V

3 phase, 3 wire: 240 volt or 480 volt or 600 volt

3 phase, 4 wire: 208Y/120 volt or 480Y/277 volt

Usually only one supply would be provided to a site (due to cost and/or availability)

The 240V is the only winding which is split (to provide 120V). The coils for other voltages are not usually split.

277 volts is convenient for fluorescent lights as it allows a simpler (cheaper) magnetic ballast

I imagine that in some cases a higher voltage supply is fed into the building and a step down transfromer is often used for 120V sockets.

Nothing more to add here this topic is well covered.

Hero999 You are correct. These bigger buildings have 277 / 480 Supplies for HVAC and lifts and certain fluorescent light fittings.
Then additional 480 / 120 Volts transformers are used to supply 120 Volts ac to power sockets.

In older parts of Europe 127 / 220 Volts may be still around, although most was superseaded with 220 / 380 and now 230 / 400 Volts.

In remote Italy a unusual voltage was around of 160 / 275 Volts.

These had all 120° between phases.