On 5/28/24 12:47, gene heskett wrote:
On 5/28/24 15:29, Roy J. Tellason, Sr. wrote:
On Tuesday 28 May 2024 01:49:52 pm Paul M Foster wrote:
I've never see a 3 phase in a house. Common in commercial/industrial,
though.
Residential installations (talking in the US here) typically involve
*one* transformer tapping a single phase out of the three that are up
there on the pole. The secondary is center-tapped, and it's that
point which is grounded at the service entrance. Running 3-phase
power requires *three* transformers up on the pole, much more in the
way of expense if you want that for some reason, and I don't know of
anybody that does that. Even those who are into having some
nontrivial machinery around seem these days to use a VFD to give them
multiple phases at the machine, rather than going through the expense
of having it run in from the pole...
And here you have it from another CET.
Cheers, Gene Heskett, CET.
AIUI in the USA for residential 120/240V single-phase three-wire service
drops, electrical utilities either run all three phases along the
distribution line or they run two phases. Running one phase and a
neutral instead of two phases would reduce the power by the square root
of 3.
Running one phase and using the Earth as the return conductor is very
dangerous and not modern practice.
David
