1 Feb
2011
1 Feb
'11
4:08 a.m.
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...
That's sad. In Sweden houses (almost?) always have 3-phase mains
(230/400V), and flats get single phase. A very large proportion of
Swedish houses have electric heating, run off 3-phase. A house will have
at least 16A, sometimes 25A meter fuses; Sweden is quite cold in winter.
Running 3 phase into a normal house is standard. The water heater will be
3 phase, usually the kitchen stove as well, and washing machines and
tumble dryers can be connected either single phase or 2, sometimes 3
phase. The lighting and power points will be distributed evenly between
the three phases (obviously).
Although my flat does seem to have 3 phase. I shall have to check, I only
moved in 3 months ago...
Jonas
2 Feb
2 Feb
10:31 a.m.
That's sad. In Sweden houses (almost?) always have
3-phase mains
(230/400V), and flats get single phase. A very large proportion of
No, it;'svery difficult to get the electicity companies to run 3 phase
amins into a house in the UK. People who want to run 3 phase motors
(medium-size machine tools, real disk drives, etc) have to use some kind
of converter, eitehr a mootr + capacitors or an electronic device.
Swedish houses have electric heating, run off 3-phase.
A house will have
at least 16A, sometimes 25A meter fuses; Sweden is quite cold in winter.
Ah, we may only have 1 phase, but the normal mains fuse over here is 80A.
Running 3 phase into a normal house is standard. The
water heater will be
3 phase, usually the kitchen stove as well, and washing machines and
tumble dryers can be connected either single phase or 2, sometimes 3
That might explain the 'optional' conactor and multi-phase wiring on our
wanhing machine wiring diagram. Did I metion it's a Swedish machine...
-tony
3 Feb
3 Feb
10:53 a.m.
> Swedish houses have electric heating, run off
3-phase. A house will have
> at least 16A, sometimes 25A meter fuses; Sweden is quite cold in winter.
Are you sure? 16A 3 phase is only 11kW, 25A 18kW. I would expect 60A
or 100A fuses.
Back in the 1970s and '80s - oil expensive, gas not everywhere - there
were a number of electric heating installations in the UK. You either
had storage heaters (basically, lots of bricks with coils of nichrome
wire running through them) or electric central heating - a tank of water
with one or two 9.6kW immersion heaters, and radiators like any other
central heating system.
In the latter case, they would run two of the three phases to the house,
and put one heater on each. Both immersion heaters came on during the
off-peak period at night, and you could switch one of them on during the
day (very expensively) if you needed extra heat.
My parents' house (re-wired in 1978) has storage heaters. Lots of them.
One winter we clocked the meter at 36kW during the brief period
between the start of off peak and our bed time...
If you haven't done the arithmetic in your heads already, that would
have been 150A had we only a single phase supply. But we have three
phases, with 100A fuses on the incomers.
Incidentally, in some rural installations, only 2 phases of the 11kV
circuit are taken to a remote village or farm. The local (usually pole
mounted) transformer connects accross the two phases and gives 230V
single phase, or, in very rare cases, 460V centre tapped to earth.
Philip.
4 Feb
4 Feb
11:03 a.m.
Philip Belben <philip at axeside.co.uk> writes:
Remember that it's three phase with a 2pi/3 phase difference. Your
calculations are only correct if we were considering three separate
single-phase supplies: 3*240*16=11.5kW and 3*240*25=18kW respectively.
If we consider a resistive load in a delta connection, which is the case
in a typical Swedish electrically heated house with 380V (the voltage
between two phases) radiators, the maximum power available is
sqrt(3)*380*16*3=32kW and 49kW respectively.
Regards,
--Frej
> Swedish
houses have electric heating, run off 3-phase. A house will have
> at least 16A, sometimes 25A meter fuses; Sweden is quite cold in winter.
Are you sure? 16A 3 phase is only 11kW, 25A 18kW. I would expect 60A
or 100A fuses.
noon
Frej Drejhammar <frej.drejhammar at gmail.com> writes:
If we consider a resistive load in a delta connection,
which is the case
in a typical Swedish electrically heated house with 380V (the voltage
between two phases) radiators, the maximum power available is
sqrt(3)*380*16*3=32kW and 49kW respectively.
Correction: That should be sqrt(3)^-1 * 380 * 16 * 3=11kW and 16kW
respectively.
--Frej
12:08 p.m.
On Friday, February 04, 2011, Frej Drejhammar wrote:
Philip Belben <philip at axeside.co.uk> writes:
Remember that it's three phase with a 2pi/3 phase difference. Your
calculations are only correct if we were considering three separate
single-phase supplies: 3*240*16=11.5kW and 3*240*25=18kW
respectively.
If we consider a resistive load in a delta connection, which is the
case in a typical Swedish electrically heated house with 380V (the
voltage between two phases) radiators, the maximum power available
is sqrt(3)*380*16*3=32kW and 49kW respectively.
You've got an extra x3 in there...
16A, 220V to ground service would give you 16A *220V * 3 = 16A * 380V
*sqrt(3) = 10.5kW. (you can treat them as 3 separate single phase
circuits if you use their voltage to ground).
They don't act like 3 x 380V single phase circuits, you actually get
less power out of them, because the currents between each leg add up
(with a phasor, so you get 1.7 x instead of 2 x the current).
Pat
--
Purdue University Research Computing --- http://www.rcac.purdue.edu/
The Computer Refuge --- http://computer-refuge.org
>
Swedish houses have electric heating, run off 3-phase. A house
> will have at least 16A, sometimes 25A meter fuses; Sweden is
> quite cold in winter.
Are you sure? 16A 3 phase is only 11kW, 25A 18kW. I would expect
60A or 100A fuses.
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5 comments
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participants (5)
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ard＠p850ug1.demon.co.uk -
frej.drejhammar＠gmail.com -
jonas＠otter.se -
pat＠computer-refuge.org -
philip＠axeside.co.uk