You are correct Jim. I just did not include the 480 V used for industrial purposes. The 3 phase 207 V is used in office buildings primarily for lighting. It is really 120 V line to neutral and 207 line to line. 207/sqrt 3 = 120.8
The 480 V line to line is used in factories to run heavy machines. 120 V for control is derived from transformers. ----- Original Message ----- From: "Jim Elwell" <[EMAIL PROTECTED]> To: "U.S. Metric Association" <[EMAIL PROTECTED]> Cc: "U.S. Metric Association" <[EMAIL PROTECTED]> Sent: Saturday, 2004-02-07 13:12 Subject: [USMA:28583] Re: Torque and horsepower > At 07 02 04, 10:26 AM, Gene Mechtly wrote: > >On Wed, 4 Feb 2004, Chimpsarecute wrote: > > > ... > > > In Germany, ... > > > > > > In the US, the 3 phases on the pole are at 13.5 kV line to line... > > > >Not true. In the US, three phase transformers are found only at > >"substations" on concrete, surrounded by wire fences. > > > >A maximum of three or four houses are served by one *single phase* > >transformer "on the pole" or, in newer housing developments, by a single > >phase transformer mounted inside a steel enclosure sitting on the ground > >and connected by underground single-phase cables. > > I'm no expert, but I do not think either of these is entirely correct, > unless this is ONLY about residential areas. > > Many industrial plants (such as the one my office is in) receive 3 phase > power. The power coming to the pole outside is 4800 volt, 3 phase. There > are three transformers on the pole, and they deliver 206 volt, 3 phase to > the building. > > When we bought a 480 volt, 3 phase piece of equipment, it was cheaper to > buy step-up transformers to get from 206 to 480 in the building, than to > have the power company install another set of transformers outside to > deliver 480 volts to the building. > > Of course, if the 480-volt equipment used enough power, we could not have > done that, and would have to have gone to the power company. > > Also, I know that transmission lines come in a variety of voltages, ranging > from 115 volt for older residential areas, to 780 volt, to 4800 volt, etc. > > Jim > > > Jim Elwell > [EMAIL PROTECTED] > 801-466-8770 > www.qsicorp.com > >
