TELECOM Digest OnLine - Sorted: Re: 25 Hz power

Re: 25 Hz power

Dale Farmer (
Sat, 11 Mar 2006 05:58:04 GMT wrote:

> In a message dated Wed, 8 Mar 2006 12:45:38 CST, jsw
> <> writes:

>> In NYC up into the 70's at least, power for two of the subway
>> divisions (BMT and IRT) was generated at 25Hz but converted to DC in
>> the field.

> Some electrified intercity railroads in the Northeast used 25 Hz
> power. There are, or at least were in the past, some advantages to 25
> Hz power for running locomotives. (Some railroads in other parts of
> the world use or used 16-2/3 HZ power.

>> However, I very distinctly remember the flicker of the
>> incandescent lamps in some of the BMT stations in the 60's, as these
>> were operated from the unrectified 25Hz source. I do remember that
>> some people claimed they could not see this flicker, but it was very
>> obvious, to me, anyway.

> This same flicker was apparent when I stayed with my parents at the
> Fred Harvey Hotel at the Santa Fe Railroad station in Gallup, New
> Mexico, in the late 1940s. It was my assumption this was built before
> there was a public electric power system in Gallup and that the hotel
> was supplied by the Santa Fe's own power plant, built probably well
> before the standardization of 60 Hz power in the U.S.A.

> In a message dated 8 Mar 2006 13:09:09 -0800,
> writes:

>> Note that for many years DC power was provided by commercial
>> utilities. Originally, Edison's power plants supplied DC. There was
>> a big fight between Edison and Westinghouse over DC vs AC. AC won
>> out.

> Most of today's power companies descended from Edison's companies and
> are still reluctant to give any credit to Nikola Tesla, who conceived
> of the far more practical (for most commercial purposes) multiphase
> alternating current now universally used. (Westinghouse bought the
> Tesla patents.)

> Wes Leatherock

Boston's subway system uses 600 volt DC for third rail and overhead
wire powered electrical trains. Washington DC's metrorail system uses
750 volt DC on it's third rail. Boston buys regualar 60 Hz power, and
converts it to DC at various substations around the system.

As an amusing sidebar, read about the marketing wars between
Westinghouse and Edison when they were battling over DC versus AC
power as the standard. One of the sort of sad ones were that both of
them made electric chairs to be used for executions. Westinghouse's
chair used DC current, because, he claimed, it was more deadly. I
believe Edison's chair used AC current, for the same stated reason.


[TELECOM Digest Editor's Note: The last hanging (as a method of
execution or capital punishment) in Chicago occurred in 1921. They
used to erect the gallows needed for the occassion in the alley on
Hubbard Street behind Clark Street at the old Cook County Courthouse.
That same year -- 1921 -- the new courthouse and associated jail were
constructed on the (then booming and showing promise) southwest side
of the city, 26th and California Avenue. They proudly proclaimed that
henceforth they would be using the 'much more humane' method of execu-
tion devised by Thomas Edison, an 'Electric Chair' as it was to be
known, and they gave a tour of it in the basement of the (then) newly
constructed county jail. On the first occassion of its use in 1922,
Mr. Edison was a guest of honor, giving a short speech about the
workings of the Chair before a crowd of civic leaders a few minutes
before it was put to use. His Chair was used for more than forty
years, with the last execution taking place, I think, in 1965 when
executions were transferred from Chicago to Joliet, IL at the prison
there. PAT]

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