I'm spanish, my english is not veri good.
Exist three-phase lines in USA of 120/208 V or 127/220 V for comon uses
(single-phase for houses and three-phase for power)??
Or alwais use single-phase lines of 3 wires 120/240 V??
A house conected to 3 wires, high votage for power - low voltage for lights
and general use, make possible connect the 3 wires of house using 2 phase +
neutral of three-phase line??
The plug Nema 14-15, make possible connect the 3 wires of house using 2
phase + neutral of three-phase line??
PD. In Spain, cohabit three-phase lines 127/220 V and 230/400 V, 50 Hz, in
Yes and no.
120/208Y, 3 phase, 4 wire, 60 Hz is very common for light commercial
installations such as shopping centers.
It is not used for residential applications,
120/240, 1 phase, 3 wire, 60 Hz is used for most residential installations.
This wiring configuration is commonly known as the 3 wire Edison
It consists of a 240V transformer secondary winding with a center tap.
Leg to leg(L1 -L2) = 240Volts
Leg to center tap (L1-N) = 120Volts.
Both are 60 Hz, single phase, not 3 phase.
If you need 3 phase power in the US, it is usually only provided in
*IF* three-phase is in use, it will be 120/208 V, not 127/220V.
Answer: "It depends". 120/240V single-phase is, by far, the most common.
for pure residential use. However, there are towns where some areas have
three-phase distribution, and a given house will have "2-of-3 phases" from
the pole, giving 120/208 V.
Note: in such locales, the customer does *NOT* have any choice as to whether
his property is served by 120/240 single-phase, or 120/208 '2-of-3 phases';
the customer gets "whatever the neighborhood is wired for".
Bigger apartment (or condo) buildings, are more likely to have three-phase
into the building, with "2-of-3 phases" going to any particular unit.
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