Yes, you got it in your hand, its that centertap for "2-phase" electricity, which it obviously should
not be called, as 3-phase is goody-goody, 2-phase not.
That is, consider two hefty loads, kindo 220V together, one on the "normal" 110V, the other one on
the "inverted" 110V, with a neutral in the middle..
The neutral, or return path, will be unecessary if the loads are exactly equal, yes??
That is, nobody notices if that neutral, center tap, is there or not.
Now hook up a little thing like a handset charger on that first "normal" 110V, and
assume the neutral is there.
Works great....
But then, consider, as all things should be considered, what happens when the usual thing
happens, something breaks down, overheats,etc..
- neutral middle tap is very rusty, almost broken, but very little current has ever passed through the
wires.
- that "negative" 110V load is almost shorted......
Oops, you got 220V over that little handset charger...
Plus a lot of other dangerous situations on the non-microsoft issue of "how does it work when
something goes wrong"
For example, in above case, not a short, but a disconnect, and suddenly that rusty neutral is
almost 110V...ouch..
Ilmarinen
3-phase is different as none of the phases, when something goes wrong, can double the voltage
of the others..
European solution:
220V (nowadays 240V nominally, as some EU countries had, like US, to boost their 220V to 240V to
ensure 220V down the line, some things don't like to brownie voltages) 3-phase to every house or household.
(ouch, need three fuses on the incoming side)
Heavy loads distributed among the three phases, as well as lightbulb loads, as well as more critical
stuff for wet areas, bathrooms, kitchen, etc..
Anyway, nothing wrong in detecting current differences between "hot" and "neutral" to detect a leak,
break the circuits, but another matter of realistic facts is that when fuses and triggers blow and break
to much, usually some handy one replaces them with a nail or similar. (me was thaught to use
a suitable thin nail)
Btw, I'm still impressed with the thunder and lightning stuff of modern US utility networks where there
really is a lot of thunder and lightning, however, some of it seems to run on wincrash or some similar
embedded system??
Background, one wise elderly guy who once (or repeatedly) informed me that
- some like to get things to work at least once
- others are proud when they work when they work
- professionals, the real guys, spend more time to make things work when they don't work, that is, fail safely.
(which seem to something behind a comet for many of the commentators on, for example,
Nokia-Sonera 3G stuff, issues like compatibility, etc,etc,etc,etc,etc...) |
