31 Jan
2011
31 Jan
'11
10:32 a.m.
On 31/01/2011 17:59, Alexander Schreiber wrote:
IIRC the trick was that the "harmonized
standard" defined 230 V as the
standard voltage with the tolerances large enough to cover pretty much all
the voltages (220 ... 240 V) that were mostly in use at that time.a
Correct, in the UK it's officially 230V +10%/-6% instead of 240V +/-6%,
but in practice it's generally close to 240V. At least it is for the
"average" consumer; someone close to the supply transformer might
actually get up to 253V and someone further down the line where the
voltage has dropped might only get 216V, and still both would be within
the limits. Something similar is true in other parts of Europe, of
course. It makes calculations and specifications of power in water
heaters and the like rather interesting: P=V^2/R so for a resistive
heater the difference can be quite large.
Likewise, people here often refer to 3-phase as 415V, but the standard
says 400V plus/minus something.
--
Pete Peter Turnbull
Network Manager
University of York