Re: [CAD_CAM_EDM_DRO] Re[1]: FYI: Home Depot Good buy on conns/cables 20' 3...

In a message dated 03-Oct-00 16:24:28 Central Daylight Time,
Ian@... writes:

<< however, what has intrigued me
is the realisation from what has been said that you may have two phase power
to your homes and, even more surprising that both phases may be available at
a wall outlet! Can this be true?? >>

Ian: I am not an electrician, but I "know more about electrical stuff than
most of them", except I often have to "read up" to find out what color wire
to use in what size box,when I fiddle with my shop- or house-electricals!
But I can throw in my stupid-Yank tuppence worth:

MOST U.S. residences have what you are calling "two-phase". Envision "three
wires", the center one being white = neutral = earth (but not "same as"
"safety-ground", although it WOULD be connected to that "at the
service-panel box"!!!). Each of the other two are usually black, and have an
AC potential difference between them of 240 VAC, 60 Hz. Either, then, is 120
VAC to that middle neutral. Our "lighting current" - wall-outlets and
ceiling-light fixtures - is 120 VAC. That 240 is usually brought-in to such
places as the kitchen, where stoves and ovens are 240 VAC, as well as
clothes-dryers (well, the ones not gas, anyway!). Most "central" (not
"window-") air-conditioners are 240 VAC, single-phase.

They are only those "big units" in large residences for folkes with so much
money they don't have to ask the price when making a purchase that have
3-phase, and THAT's often interesting! There, you have "balanced 3-phase",
any one of the three legs to neutral being 240 VAC, or about 415-416
"nominal" between any-two of those three. This is used in industrial sites,
etc. Here, we have a similar system, but exactly-half, i.e., each of the
three phases to neutral is 120 VAC, our "lighting voltage", but 208 V.
between one-another. I guess MOST small industrial shops have this "balanced
3-phase". (our 416 V 3-phase is found only in larger installations where
SERIOUS machinery with, say, 50 hp motors are found).

But we have a perhaps-unique 3-phase system, here, as well, the "Open Delta"
connection, where that "tapped" transformer is used for both "lighting
phases" as described above, but a second transformer, fed from a SECOND
high-voltage primary "on the pole" is supplying the "third phase", called the
"high-leg". Why "High"?? Because it measures about 200 V. to neutral,
whereas the other two measure 120 V. to neutral; yet, that, and those other
two measure 240 V. (no, NOT 208 V.!!!) between one-another! Thus, "three
phase motors" are often supplied with different wiring-taps for connection to
EITHER 240 V-3-ph. or 208 V-3-ph.! Some are specified "208-240 VAC,
3-phase".

Though a dum' ol' Yank, I have had an opportunity in recent decades to build
a large machine for an English firm in Suffolk, and it had to have large
3-phase machines on/in it, so, I had to "read-up" and learn about these
details before I shipped 4000 lb. of iron to England which wouldn't work
anywhere in the world, because I had ordered a motor from Germany for use in
England, but installed on the machine in Texas, first! Lemme TELL ya, I
learned, "Never again, anything larger than a breadbox!"

<< I have long marvelled at your choice of wire colour schemes which I see
almost daily on 'Home and Leisure' channel in the 'This Old House' series and
others, and at the quaint way you still use what we used to call 'screwits'
to join wires - a method which was banned in the UK in the '60's. However,
the idea of having two phases - in your case 220v, for the home
mechanic to play with is just too intriguing. Perhaps the idea is sponsored
by home appliance makers who can benefit from the smoke-making skills of
amateur electricians? >>

Hmmm... Ain't it a small world! I liked that same show, here, for years,
until money dictated that it be replaced by "Suzy's Quilting Circle" or
some-such! House-wiring colours? I only know of black (hot) and white
(neutral), which, in Europe, are brown and blue, resp. Oh, and your green
with yellow stripe is generally only green, here, but SOMEtimes with the
yellow stripe, if made in Japan or imported, or built by a firm which often
exports!

If you have any specific questions, or just wanna chat, on-line, feel free!

Jan Rowland, Yank Troll with attitude!