They used to give tours to the 1MV DC transmission station in L.A. - Edison lives.
I would have loved to have seen the original Hg arc valves. Brian > -----Original Message----- > From: [email protected] [mailto:[email protected]]On Behalf Of > [email protected] > Sent: Monday, July 20, 2009 12:58 PM > To: [email protected] > Cc: [email protected] > Subject: Re: [PSES] Normal power supply Sweden & Norway > > Edison himself designed the US residential power system. As > inventor of > the light bulb he experimented with his carbon filament > technology and > determined that an optimal filament required ~110V. Recognizing that > distance was an issue for his DC generating stations, he designed a > system that used 220V with a center tap. Inside a residence > loads are > placed approximately half on each side of the supply. The center tap > only has to carry the difference current to assure a steady > 110 V on each > side of the split. This allowed it to be relatively light > gauge which > saved on copper expense. Heavy appliances simply bridge > across the full > 220V supply. So there you have it: the distance advantage of 220V > applied to 110V lamps. Long ago a nation wide survey of household > voltages was taken, and the average was 117V. This became the US > domestic standard, since rounded up to 120/240V. > > On a side note, incandescent lamps last much longer on DC. > With AC you > have the slight but constant of temperature cycling on each > half cycle of > current, plus the slight but constant mechanical flexing by > alternating > magnetic interaction with the earth's own field. It can make a > difference whether the filament is north-south or east-west! > > Orin Laney - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
