On Fri, 6 Jan 2017 20:06:19 -0500, Ed Pawlowski wrote:

On 1/6/2017 3:52 PM, Leon wrote:

Oddly I think 440 volt is still normal

Unless is is 480

I read the explanation once but still don't get 277 volts from 2 legs of
3 phase.

It's the opposite. 277V is a single phase of a 480V phase-to-phase
system. This is entirely different than a 120V system (a transformer
is required to get there).

https://ctlsys.com/electrical_servic..._and_voltages/

The nominal 120 was decided as the standard for north America but I'm
not sure when. Voltages were 110, 115, 117 in different places some
years ago.

Yes, I'd forgotten 117V.