TELECOM Digest OnLine - Sorted: Re: 25 Hz Power

Re: 25 Hz Power

Garrett Wollman (wollman@csail.mit.edu)
Fri, 10 Mar 2006 22:31:25 UTC

In article <telecom25.97.13@telecom-digest.org>,
<hancock4@bbs.cpcn.com> wrote:

> I don't know if true, but someone told me that in Europe they didn't
> bother with three phase for house supply, but just give everyone 220
> service. That does seem to be more efficient for house supplies.

This paragraph doesn't make any sense.

The standard residential supply in Europe is 400 V three-phase wye,
with 230 V nominal on each leg, at 50 Hz. In the UK it is actually
415Y/240, but the standard includes enough slop to allow it.
(Similarly most other European countries' "230" is actually 220.) In
some locations, rather than drawing all three legs into each
residence, neighboring dwellings may get single-phase feeds from
different legs.

The standard residential supply in North America is 240 V single-phase
center-tap, with 120 V nominal on each leg, at 60 Hz. However, some
residences, particularly in New York City, have 208 V three-phase wye
with 120 V nominal on each leg, still at 60 Hz. Commercial office
buildings in the US often have 480Y/277; commercial lighting often
operates on 277 V, and blowers, compressors, elevators, and pumps
often use 480 (either wye or delta). Power companies can also supply
600Y/347 for medium-size industrial customers.

I don't know how they do it in Japan, but with 100 V nominal supply I
would assume they do either the center-tap hack or three-phase in
order to supply high-power devices at lower current.

Garrett A. Wollman | As the Constitution endures, persons in every
wollman@csail.mit.edu | generation can invoke its principles in their own
Opinions not those | search for greater freedom.
of MIT or CSAIL. | - A. Kennedy, Lawrence v. Texas, 539 U.S. 558 (2003)

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