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From: jgk@osc.COM (Joe Keane)
Newsgroups: sci.electronics
Subject: Re: 50 Hz in Europe... Was the decision political?
Keywords: frequency
Message-ID: <1762@osc.COM>
Date: 23 Dec 89 13:04:22 GMT
References: <1242@bio73.unsw.oz> <10481@etana.tut.fi>
Reply-To: jgk@osc.osc.com (Joe Keane)
Organization: Object Sciences Corp., Menlo Park, CA
Lines: 40

From an ancient tome:
%The standard of frequency in North America is 60 cycles per second.  In most
%foreign countries it is 50 cycles.  As a general-purpose distribution
%frequency 60 cycles has an economic advantage over 50 cycles in that it
%permits a maximum speed of 3600 rpm as against 3000 rpm.  Where a large
%number of distribution transformers are used a considerable economic gain is
%obtained in that the saving in materials of 60-cycle transformers over
%50-cycle transformers may amount to 10 to 15 percent.  This is because in a
%transformer the induced voltage is proportional to the total flux-linkage
%and the frequency.  The higher the frequency, therefore, the smaller the
%cross-sectional area of the core, and the smaller the core the shorter the
%length of the coils.  There is a saving, therefore, in both iron and copper.

It is interesting to me that our electricity standards come directly from the
fin-de-siecle work of Tesla and Westinghouse.  With the exception of some
very-high-end DC transmission, all power transmission and distribution is 60
Hertz, three-phase (with single-phase subsets).  Certainly this was a good
choice at the time, when transformers were high-tech and no one had heard of
semiconductors.  I wonder what the power system would look like if it were
designed from scratch today.

Maybe it would use 400 Hertz.  This results in large weight savings in
transformers.  It's also quite a bit safer; you're more worried about getting
burned than having fatal muscle contractions.  Then again, reactance and phase
shift become much more of a problem.

There might be more use of DC.  Almost anything electronic really works on
low-voltage DC.  But i don't think people are going to run +5 VDC through
their houses though.  Imagine going to the store to buy a new 1000 amp fuse!
Then again, i have seen a lot of new 12 VDC lighting systems.

Getting less radical, a while ago there was a kick to run 240/416V services to
new houses.  The idea was that big stuff would use the three-phase or 240V
line-to-ground, and a small utility-owned autotransformer would supply a 120V
phase as normal.  The utilities would win big becuase they'd have less copper
and lower losses in their secondaries.  They also get better phase balancing
from more three-phase loads and being able to switch each house's phase
independently.  I don't know what happened to this though.

Anyone else have thoughts on these things?