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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: net.analog
Subject: Re: Some answers, some questions
Message-ID: <227@kitty.UUCP>
Date: Sat, 3-Aug-85 11:52:52 EDT
Article-I.D.: kitty.227
Posted: Sat Aug  3 11:52:52 1985
Date-Received: Mon, 5-Aug-85 00:33:25 EDT
References: <254@unccvax.UUCP>
Organization: Recognition Research Corp., Clarence, NY
Lines: 48

> > Why are the standard worldwide AC line-voltage frequencies 50 or 60 Hz?
> 
>     Was there ever a 25 Hz standard in the U.S. ? I  remember
>     old Sears catalogues mentioning that their power tools were not
>     'for use in Chicago where there was 25 hz current.' 

	Not only was 25 Hz the first U.S. standard power frequency, but it
is still used in many parts of the country, especially the eastern states,
and in particular New York State!  All of the first major industrial plants
had 25 Hz.  As 60 Hz (there was also some 50 Hz here) became common in the
1920's, the 25 Hz frequency remained for heavy industrial loads.  A *great*
deal of industrial construction occured between 1910 and 1930, all of which
used 25 Hz transformers and switchgear. While almost no new 25 Hz installations
occured after 1930, the major industrial plants already in place expanded and
perpetuated the use of 25 Hz.
	Believe it or not, there are *many* industrial 25 Hz motors still in
service; some of these motors are over 60 years old and still running.  I am
talking about LARGE motors, like 100 hp to 5,000 hp whose replacement cost
with 60 Hz counterparts would be enormous.  As a result of pressure from large
industrial customers, 25 Hz is still distributed in many areas.
	I personally know of several chemical plants in Niagara Falls, NY
[ home of the Love Canal :-) ] which get 128 kV 25 Hz primary service.  I have
seen installations where live front (i.e., knife switches) power switchboards
handling 550 volts 25 Hz still exist today.  Since they are 'grandfathered',
the only concession to OSHA is a guard rail.
	At one plant where we do consulting work, they have a 4160 volt 2 MW
60 Hz primary service.  In addition, they have a 200 amp 220 volt 25 Hz
service (which is absurdly puny by comparison!) just to run some freight
elevator motors.  The plant was built in the 1920's, and while they have
converted to 60 Hz for everything else, they have kept the freight elevators
25 Hz since a conversion cost would require total rebuilding of the elevators
at a cost of well over $ 100K.  As long as the power company continues to
offer the 25 Hz service, they have no incentive to convert.  At this time, the
power companies are obligated by tariff to supply all existing 25 Hz services.
Believe it or not, the power company offered them a $ 10K credit if they would
discontinue the 25 Hz service, but the company refuses.  I guess I can't blame
'em.

	Larry Lippman
	Recognition Research Corp.
	Clarence, New York
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