31 Jan
2011
31 Jan
'11
12:14 p.m.
In the US, two separate 110 legs are delivered to the house. When we
need 220, the magic of constructive interference is applied, and we
get 220. The 220 is delivered to the appliance as two separate 110
wires, a neutral wire, and sometimes a separate ground wire for
safety.
I was under the impression that the US mains was in fact 220V (or 230V,
234V, depending on which reference you believe), centre-tapped. The
centre-tap is the 'neutral' wire and is connected to earth ground at one
point. The outside 2 ieres are this 110V with respect to neutral, but as
they're in antipahse there's 220V between them. Most devices are 110V and
run between one live/phase wire and neutral, high-power stuff (cooking
ovens, tumble driers, etc) run their heating elements between the 2
outside wires so as to reduce the current they draw.
Because of this arrangement, sometimes appliances (I
believe, maybe
I'm wrong) will pull 110 from one of the legs to power electronics in
the appliance.
I beleive you are corrrect. IIRC the timer of a cooker or tumble drier,
possibly the motor of the latter is run from 110V -- between one phase
wire and neutral.
But I think european 220 doesn't work this way. Is one 220 leg
delivered to the house? And the electronics work off that 220 leg?
Yes, exactly. The domestic mains is nomianlly 230V now. We get a single
phase wire and a neurtal, the latter being close to ground. Everything is
designed to run off that 230V supply. There is no 'centre tap'. So our
cookers, say, have 230V elements and a timer that runs off 230V mains.
Actually, the European mains is 3 phase. The final transformer secondary
is start (wye?) connected with the star point being th eneautral. Houses
get a single phase supply consisting of that neurral wire and one of the
phase wires -- to balance the load, neighbouring hosues in a road get
different phases [1]. Of coruse industral places get the full 2 phase
mains to run larger motors, etc. It's very difficult to convince the
electricity companies to run 3 phase mains into a normal house, though,
which is a problem for people who ant to run large disk drives ;-)
[1] In the cases of blocks of flats, student halls of residence, etc,
it's not unheard-of for each floor to be wired to wired to a different
phase. This has led to studend running extension leads to the rooms above
and below theres so as to get a 3 phase supply...
Or are two 110 lines delivered and every outlet gets
the sum of those
two 110 lines?
No, if we ant 110V, we have to provide our own step-down transfoemr
If it's not two separate legs, I'm thinking that it will be impossible
to wire an american 220 appliance to work with european 220. Is this
right?
It depends on what yuou are trying to do. Certainly a US appliance that
needs 110V for any function is not going to work on European mains
without modifications. That may be as simple as providing a small
step-down transofrmer for the control unit supply.
Waht are you trying to do?
-tony