TELECOM Digest OnLine - Sorted: Re: Tie Lines was Re: Foreign Exchange (FX) Lines Still in Use?

Re: Tie Lines was Re: Foreign Exchange (FX) Lines Still in Use?

Robert Bonomi (
Sat, 28 May 2005 09:37:57 -0000

In article <>, <> wrote:

> Robert Bonomi wrote:

>> In article <>,

>>> [TELECOM Digest Editor's Note: City of Chicago used DC power (rather
>>> than AC) -- at least in the downtown area -- until sometime around
>>> 1930. That's at least one reason why there were so many WUTCO clocks
>>> everywhere, instead of 'regular' wall clocks. Clocks cannot run on
>>> direct current; they require alternating current at 60 cycles.

>> I wonder what they did in territory where the generated A.C. power was
>> at 25 cycles.

> When did they deliver AC at 25 cycles? I do recall some 50 cycle
> companies around that had to change after the end of WWII.

I don't know when the last 25-cycle power was phased out. Keokuk, Iowa,
had a 25-cycle hydroelectric plant -- driven by the Mississippi River,

As of the early 1960s, the hydro plant there was dark, although equipment
was still in place. Power distribution to users was 60-cycle at that time.
I'm _guessing_ conversion was late '40s, early '50s.

"Carnegie-Illinois Steel Company" was running their own electric
generators at 25 cycles at least through the mid '40s -- in '43 they
installed a 'mercury-pool' frequency conversion system that let them
feed their power into a 60-cycle public utility power distribution

One of the down-sides to 25-cycle power was that _transformers_ had to
be built heavier for the lower line frequency. Stuff that was build
with the existence of lower frequency power worked just fine when
connected to a higher-frequency source. Unfortunately, when you took
something that had been designed to be 'just adequate' on 60-cycle
power, and plugged it into a 25-cycle source, a frequent result was
'letting the magic smoke' out of the transformer. A *RUDE* surprise
for someone who moved into one of those 25-cycle 'islands' from the
mainstream of power distribution.

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