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

Robert B>> 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 network.

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.