electric supply in the USA
electric supply in the USA
(OP)
Hi everybody,
could anybody tell me what kind of electric power Voltage I can expect to encounter in the US (single phase and 3 phase).
Also I would like to know what kind of tolerances I have to expect since the situation seems to me a little wilder than in the EU
If what I have heard is right in some places the Voltage is much higher and in some other wuch lower than what it is supposed to be.
Thanks
Luca
could anybody tell me what kind of electric power Voltage I can expect to encounter in the US (single phase and 3 phase).
Also I would like to know what kind of tolerances I have to expect since the situation seems to me a little wilder than in the EU
If what I have heard is right in some places the Voltage is much higher and in some other wuch lower than what it is supposed to be.
Thanks
Luca






RE: electric supply in the USA
In general, the 3 phase distribution is 208Y120, 230V delta or 480Y277. There are also plenty of variations to that, such as 230/120V Red Leg Delta, 230V Open Delta, 460V Delta etc. etc. All of these are "nominal" voltages, meaning that 208V may be 200V, 230V may be 220 or 240V, and 480V may be 460V.
Single phase is always 120/240V, but it may be 115/230 or 110/220 depending on the area.
Then you have some areas where they have 575V, and 1 or 2 others that still have 25Hz systems!
Tolerances are generally +-10%, but for instance if they supply 200V 3 phase, they generally will not allow that to go down to 180V because the 200V was already essentially 208V with some of the margin already used.
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
RE: electric supply in the USA
RE: electric supply in the USA
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
RE: electric supply in the USA
Thanks for that.
RE: electric supply in the USA
I did get to work around some 2200V 25Hz wound rotor induction motor controls that were being replaced in Spokane Washington after 90 years of operation. Everything was yanked out and the new equipment was connected up to the 60Hz grid. The hydro generators, pumps and controls were built by Westinghouse in 1906, we replaced them in 1996. Controllers were the old open knife switches on giant slabs of slate, with uninsulated bus bars running around everywhere. One room where the resistor banks were located was so filled with open bus bars that it was called the "suicide room"! I have pix somewhere, but from the pre-digital camera days. If I ever get around to finding and scanning them, I'll post them.
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
RE: electric supply in the USA
Can't most of the 25Hz motors be run through VFDs at 25Hz then when the motor finally croaks drop in a 60Hz? Spoze the 25Hz motors aren't rated for inverter duty!
RE: electric supply in the USA
RE: electric supply in the USA
RE: electric supply in the USA
"Also I would like to know what kind of tolerances I have to expect since the situation seems to me a little wilder than in the EU
If what I have heard is right in some places the Voltage is much higher and in some other wuch lower than what it is supposed to be."
This is just a WAG but somewhat in defense of North America and I'm sure I'll be told if its kooky. The EU was/is much smaller and more densly populated than NA. Line losses play a bigger role in tolerances here. Ie. originally, single phase was to be 110/220 Vac. When you got to the end of the line it was more like 100/200. So they boosted it to 115/230 and then to 120/240. Now in some areas one can measure 130/260.
So if one is lucky enough to live nearer the front end, kitty gets his food quicker cause the can opener runs a tad faster, but its life is a few monthts shorter (the can opener). U get the drift?
Cheers
Life is what happens while we're making other plans.
Wally
RE: electric supply in the USA
You are essentially correct BWB, but of course, you imply some intelligent design in all of that, and I doubt it wasn't that organized. As electrification demand grew prior to WWI, utilities sprang up in urban centers all over, each with their own solution to distribution problems. As they began to overlap, standards arose that blended some of those solutions with compromises all around. With the REA in the 30's, some semblance of order began to emerge but still there are different problems to overcome in every area, with varying solutions. We continue to struggle with that diversity to this day.
rcwilson,
Are you referring to that specific room at the hydro works in Spokane?
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
RE: electric supply in the USA
Gunnar Englund
www.gke.org
RE: electric supply in the USA
Bye
Luca
RE: electric supply in the USA
RE: electric supply in the USA