There exist copies of newspaper and magazine ads for home radio
receivers (RCA and others) that were built specifically for the DC
residential distribution of New York's Central Business district. The
ones I've seen were from the 20's and 30's.
I'm not sure when this DC service was discontinued, although I seem to
recall that Con Edison provided DC service for elevators well into the
50's and maybe beyond.
I'm sure someone here has the details...
They still do supply DC in NYC. but I think they are trying to phase it out.
As a first step:
my guess is within 10 years they will try to have all DC systems supplied as
AC to the customer and then customer rectified.
I may be wrong, but I thought there was an article in one of the IEEE
magazines a couple of years ago about the last DC feeder being removed. It
was a big deal at the time. I will see if I can find it.
Benjamin D Miller, PE
Someone previously posted an article
November 14, 2007
"Today, Con Edison will end 125 years of direct current electricity
service that began when Thomas Edison opened his Pearl Street power
station on Sept. 4, 1882. Con Ed will now only provide alternating
The London cinema/theatre area had a 220VDC supply for years,
to power the arc lamps used. The University College London
Physics Department also took this and the building was wired
with 220VDC outlets (in addition to 240VAC and 12VAC outlets)
throughout, for powering experiments. I recall using the 220VDC
supply for an experiment to measure the temperature of a carbon
arc. In 1980 when I was there, the 220VDC supply was generated
in the basement as the external supply had been discontinued by
then, but I believe that only happened 2 or 3 years before,
which would be late 1970's.
[email address is not usable -- followup in the newsgroup]
On 11/4/07 7:33 PM, in article 9awXi.178406$th2.125346@pd7urf3no, "Don
Thanks for the information. I was pretty sure someone here would know.
I have been away from New York City, except for short visits, for over 50
years. I do remember motor-generator sets for running x-ray machines. I also
was aware that buyers of sewing machines in the New York needle trades
needed to worry about ac and dc. IIRC, especially with my limited knowledge
of that time, dc machines would use some form of resistor speed control and
start-up. I think that ac machines had their motors running continuously and
engaged by clutches.
I have a suspicion that it may take well over ten years to complete
conversion to ac.
The last 25Hz rotary converter substation on the Subway was shut down
in 1999, this would have been the last low frequency supply, and I
have a feeling that I read somewhere that Con Ed stopped supplying
their last customers with d.c. at about the same time.
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