OK, I just have to get my two cents in regarding electrical services in
the U.S.
There are still quite a few 120 volt, single phase residential services
in use that have never been converted to 240 volts. 240 volt single phase is
the most common residential service, but there is no standard amperage.
208/120 volt, 3 phase is commonly used for small commercial buildings.
480/277 volt, 3 phase is commonly used for medium to large commercial
buildings.
240/120 volt, 3 phase services are delta systems with a 210 volt stinger
leg. These are occasionally found in old commercial or industrial buildings
in my area, but the local utility is gradually phasing these out. The
stinger leg can be used on 240 volt, 3 phase loads, or on 208 volt, single
phase loads when accompanied by the neutral conductor.
Higher voltages are frequently used in large facilities or campuses, and
many other types of systems are used for the specific needs of manufacturing
facilities, but these should be of no interest to hams.
Jim Smith, KQ6UV
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