On Jan 4, 5:27*am, Terry Casey wrote:
In article ,
says...



In message , Geoffrey S.
Mendelson writes:

The UK used several systems, and a friend of mine who traveled to London
in the 1970's found that there were four different electrical systems in use
in various parts of the city. By that time they had been standardized to
240 volts 50Hz, but the older plugs and lightbulbs (different ones for
different systems) remained.

Your friend sounds confused. The 240/50 was standardised a long time
before 1970, and the various plugs and bulbs had been running on 240/50
for some decades by then.

I remember a major upgrade taking place in West Ham to upgrade the
distribution network from 215V AC to the standard 240V while I was at
school there in the late 50s.

Nearby Ilford still had 200V DC, a hangover from when Ilford town
council generated 600V DC for its tramways and obviously found it
convenient to stick to DC for domestic supplies.

When it was converted to 240V AC I do not know but there was no evidence
of anything remotely DC connected when I moved there in the early 70s.

In the US there were 25 Hz buildings and even houses as late as the
early 70s and a few DC apartment and office buildings in New York
later than that. I stayed at a swank highrise in Chicago in the early
70s that was AC by then but was originally DC and there was evidence
of it in the labels tacked in the fuse box.

We also had a little 50 Hz before the war.

I've always wanted to do a full study of DC and odd frequency power
historically in the US but the research is not helped by the
electrical utilities. I think they are ashamed of it.