Re: [CAD_CAM_EDM_DRO] Re: U.S. 220 vs Euro 220

In a message dated 17-May-01 14:00:34 Central Daylight Time,
info.host@... writes:

> What is Star and Open Delta (?Wye?)? Do you remember where abouts it was
>

Someone else with more experience in the topic (i.e., licensed, degreed
electrical-engineer) will probably have answered this already, but here's my
tuppence worth, anyway:

First question: "Star" and "Open Delta" and "Wye" are implicative of
transformer connections (secondaries) that output the 3-phase to your house
or shop (if you have 3-phase lektricity at home; few do!). The "Star" and
"Wye" are the same thing, just different words. See Letter "Y". The three
"tips" are the "legs" of the 3-phase power, and the junction of the "three
pieces" of the "Y" is neutral. In the USA, if you have "Wye" 3-phase, you
would measure 208 VAC between any-two of those "tips", and 120 VAC from any
one of them to that neutral (which is electrically connected to "ground" as
well). SOME industrial service (bigger factories) in USA might have 416 VAC
"between legs".

"Open Delta" is USA-only, and is generally found in smaller "industrial
parks" or for customers such as office-buildings, schools, LUCKY home-shops
to which the electrical utility agreed to feed 3-phase (cost ME $1550 to get
extant transformers enlarged to serve ME and the school, next door!). OPEN
delta? Yes. A "delta" is an equilateral triangle. Imagine you remove one
side. Then center-tap the horizontal leg. That center-tap is "neutral", so,
you would have 120 VAC from that neutral to either end of that horizontal
leg, and 240 VAC between those two ends, for your stove and air-conditioning
machine, if it's single-phase, as it probably is. The ONE leg "at an angle"
is connected to one end of that horizontal leg, but the OTHER end is the
"high leg" (if measured with resp. to neutral, it'd be some odd voltage like
197 or 200 volts, but that single-phase connection is NEVER used alone). So,
your two ends of that horizontal leg are two of your three phases, and that
"high leg" is the third one. They measure 240 VAC between any-two of them.

440 VAC single-phase is not used in homes. It may be used for some
industrial purposes, but I am guessing ONLY as a three-phase supply, not
single-phase.

In England, the "lighting voltage" is 240 VAC/50 Hz. nominal. Their 3-phase
is 416 VAC (but they "call it" 415 VAC). On the Continent (Germany, France,
Holland, etc.), the "lighting voltage" is nominally 220 VAC/50 Hz, and their
3-phase is about 385 VAC between legs. I learned all about this when I built
a huge X-Y table with a 3.5 hp/400 Hz./3-phase router on it (controlled by
PC). That "quill" was powered by a motor-generator that ran off the UK's
415VAC/50Hz. (the postal-code changed each time that was switched on!
Whew!). That quill-motor and power-converter-generator were built in
Germany, thus the "instant education" about voltages, etc.

Someone on this thread mentioned that UK is "trying" to lower the nominal 240
V. to 230 (surely to more-nearly "match" the other EC voltages), but if this
is so, NO evidence of that existed in '86, when I did the work in England!
There, the "nominal" 240 VAC WAS! No "light-dimming" when a large-HP machine
was switched-on! Kudos, small-town-in-England! Here, if a Dairy-Queen
fridge switches on a block away, the lights flicker! Keeping digital clocks
set is a grand chore! And California complains! Damn hippies!

Next?



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