TELECOM Digest OnLine - Sorted: Re: 25 cps Power, was: Tie Lines was Re: Foreign Exchange Lines

Re: 25 cps Power, was: Tie Lines was Re: Foreign Exchange Lines

hancock4@bbs.cpcn.com
31 May 2005 09:22:31 -0700

Paul Coxwell wrote:

> Somebody else recalled that when his grandfather worked as an
> electrician in the West Virginia mines in the early 1950s that they
> had 25Hz power.

For some reason, when AC was to be used (needed for transmission
efficiency), 25Hz was required for electric motors back in the 1920s
and 1930s. It was widely used in railroads. The electric trains from
New Haven to Washington DC, west to Harrisburg, and on numerous
branches serving commuters, was all 25 Hz, and much of it remains 25
Hz to this day.

Subways used 600 V DC, but purchased or generated 25Hz power and sent
that out to the substations for rectification and voltage
transformation.

Because of the above, for years certain commercial power stations
continued to generate 25 Hz for their railway customers. I think now
they finally are able to use solid-state converters instead of the big
rotary machines. As mentioned, some railroads (but not all) switched
to 60Hz.

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