Michael Stone <mst...@debian.org> writes:
> On Tue, Jul 30, 2019 at 02:15:44PM -0500, David Wright wrote:
>
> On Tue 30 Jul 2019 at 08:49:43 (-0400), Michael Stone wrote:
>
> On Mon, Jul 29, 2019 at 08:46:36PM -0500, David Wright wrote:
> > On Mon 29 Jul 2019 at 18:00:25 (-0400), Gene Heskett wrote:
> > > On Monday 29 July 2019 17:26:17 ghe wrote:
> > > > On 7/29/19 1:57 PM, David Wright wrote:
> > > > > Irrelevant in a domestic setting: it's illegal to have
> more than one
> > > > > phase in an ordinary house.
> > > >
> > > > FYI, and significantly OT:
> > > >
> > > > I don't think that's true in the US.
> >
> > IIRC Joe's in the UK. 3-phase there is lethal. 1 is bad enough.
>
> Domestic 3 phase is common in much of the world, including
> (specifically) the UK. There's nothing illegal about it, it's just
> prohibitively expensive if (as in most of the US) 3 phase isn't
> already provisioned. (E.g., in my area many people would need to
> eat
> the cost of more than a quarter mile of new poles and wires if
> they
> wanted 3 phase, and there's basically zero advantage unless you're
> trying to run industrial electric motors in your house for some
> reason.)
>
>
> [snip]
>
> Perhaps someone living in the UK who actually has more than one phase
> in use in their home could give some details of how it's dealt with.
>
>
> In Europe they do commonly have 3 phase supplies
>
>
>
> I did a cursory check and found UK manufacturers of things like 3 phase
> domestic stoves and assumed they were used in the UK. It seems that
> they're
> for use elsewhere in EU, so I'll withdraw that 3 phase is common in UK.
>
>
>
> but I think that's
> partly because they have lower current ratings on the phases.
> I can't speak for what their wiring regulations are like, but I
> suspect that only one phase is used for general wiring, with
> dedicated circuits to items like ranges. Even if you were to put
> different phases on different floors, you have the stairs to
> consider.
>
>
>
> Why would having different phases on different circuits be a problem? It's
> pretty common IMO, because you want the load balanced between them.
> (Unless
> the concern is that the crazy UK circuit loops will get crosswired?) In
> general 3 phase is only used for dedicated equipment circuits, but that's
> because not many portable appliances need that much power.
I did read once in "QST" which is an amateur radio
magazine, an article by an amateur radio operator who had lived
in Tehran during earlier times who wrote that some residents
there had multiple power lines and meters at their houses and a
large switch that one could move to which ever line was supplying
the most reliable source of power that day.
Apparently, multiple companies had infrastructure all
over Tehran or at least parts of Tehran, each one selling power
to anyone who could pay. No word as to whether this was phased
power but each customer would have only been using one phase at a
time so it technically didn't matter. One just used whichever
feed was working that day and switched phases or feeds when the
lights went off.
Between 1989 and 2015, I worked for Oklahoma State
University's IT Center in Network Operations. The campus has
3-phase AC power to run air handling systems in the larger
buildings, one of which was the one I worked in which held our
IBM main frame.
One fateful day around 1990 or so, we lost at least 1 of
the 3 phases which created a monster mess to say the least.
Since 3-phase motors get power from all 3 phases, the
absence of one phase means that the remaining 2 phases are
essentially back-feeding the rest of the network through all the
3-phase devices that are attempting to still run on the remaining
2.
The missing phase had transformers on it that supplied
power to offices for traditional uses such as the workers' PC's,
coffee makers, etc. Now, all those things were getting generally
lower voltage than they should but it could rise to higher than
normal at any time depending on whatever 3-phase motor was trying
to run.
I remember stepping in to a large room we had which was
full of rack-mounted power supplies which ran our campus data
network of RS-232 serial devices. Remember this was 1990 and
network communications didn't even remotely resemble what they
are today.
There were racks and racks of switching power supplies
that ran this data network and each supply was attempting to
still run. The chopping oscillators in those supplies normally
chopped at ultrasonic frequencies in the range of 100 KHZ or
more but that day, there were probably only receiving 20 or 30
volts at the power socket so they were oscillating at very
audible frequencies like so many derange smoke alarms, rising and
falling in pitch in an eerie wale.
Our serial RS-232-based network seemed sophisticated at
the time with battery backup of each node and so forth but that
sustained period of low and varying voltage convinced the
processors in the nodes that someone was changing baud rate and
loopback settings so, when the phase was restored and the normal
world returned, that network was fouled up beyond recognition for
quite a long time.
We got the nodes back by reloading each one with saved
backup files so that wasn't so bad but some of the weirdness was
propagated to nodes in other buildings so we didn't get it all
cleaned up for literally weeks. It was mostly okay that
afternoon but we would get calls from departments across the
university that this or that printer or VT100 terminal wasn't
working when somebody tried to use it and the fault turned out to
be another randomly deconfigured port.
The down phase created an apocalyptic scene what with
overhead lighting mostly absent but occasionally trying to
flicker on and the wailing power supplies.
Martin McCormick WB5AGZ
