20 Mar
2011
20 Mar
'11
2:27 a.m.
Eric said:
There are certainly other 3-phase voltages used in the
US. Probably the
next most common are 277/480 wye or 480 delta.
Oh, I see. Thanks, Eric! I was wondering what 277V was, but I had
always assumed it was the line voltage, since that is what usually gets
quoted.
FWIW in rural parts of the UK, it is common to take just two phases of
the HV (11kV) network on some spurs. You then get a single phase
transformer from 11kV to 240V. For larger loads, 11kV/480V used to be
common, with a centre tap to earth like the US 240V stuff, but this is
dying out.
Jochen said (in a post I didn't get):
In Germany, well, most if not all of Europe, the
entire power grid
is three phase. The power that gets distributed to a house is always
three phase 230 / 400 V in Y configuration. Single phase loads like
ordinary power outlets are wired from one phase to neutral. The
single phase circuits in a house (apartment, flat, ...) are spreed
across all phases to spreed load. Biger loads like electric stoves,
water heaters, big motors, ... are allways three phase. So we have
three phase in every household.
In the UK, single family houses are more common than on the continent.
Except in rural areas (see above), three phases are run down the street,
but each house gets a single phase supply from one phase and neutral.
Engineers who have worked on LV installations tell me that no matter how
carefully you specify the pattern of which house connects to which
phase, the installers will connect to the phase that is easiest to get at...
Even large electric cookers and water heaters are single phase here.
Well, water heaters above 10kW usually need two phases, but those are rare.
Blocks of flats, and my parents' house, have three-phase supplies, but
each flat generally gets just one of the phases and the neutral, so that
no-one is exposed to 415V.
(My parents have electric storage heaters, and when these come on at
night, the house draws 50A from each phase. But apart from the heaters,
everything in the house is on the A phase, and everything in the annexe
is on the B phase.)
Philip.