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Voltage Systems in the US compared to Europe 1

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TheJaxx

Electrical
Feb 16, 2007
3
Hi,

I'm an electritian from Germany. My company is building a new plant in the US and I'll be sent there.
The thing I don't understand is the voltage systems.

Here in Germany (and Europe) we generally have 3 phases. 230V/400V. In the US it's 120/240V, right? So what about the 480V? Is that a different voltage system with a seperate wireing? And what is the voltage between phase and neutral?

Thanks guys

Marc
 
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Three phase 480/277 V is common in industrial plants, as is 208/120 V. (Note: the first voltage is line-to-line, the second is line-to-neutral.) 240/120 V is more common in residential applications and is single phase, though 120 V is often found in control wiring in industry.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
 
240/120 is also a three phase delta voltage. Either open delta or closed delta. One phase has the center tap brought out to supply 240/120 single phase loads. The center tap is grounded.
respectfully
 
Also most commercial and light industrial buildings have service voltage of 480Y/277V and 208Y/120V is derived using step-down transformers. 480/277 is used for most mechanical loads and 277 is for lighting in commercial/industrial facilities. 120 is mainly used for convenience wall outlets or office equipment (computers, plug and cord devices etc., they are always 120V)

Residential is strictly 240/120 or 208/120V. Even there 208 or 240V is resricted to heavy appliance like range, A/C unit and dryer only. Residential lighting is always 120V.

For certain special use facilities like hotels ,nursing homes and hospitals you need to check NEC in the USA.
 
If you do work in Canada, you will also encounter extensive 600/347V for industrial/commercial applications used wherever 480/277V is used in the USA.
 
Yes Jaxx,

USA uses all possible versions of transformer connections - many of which you wouldn't believe. There is a good summary in Siemen's "Schalten, Schuetzen, Verteilen in Niederspannungsnetzen"

Also, be prepared to see TT systems - separate grounds at transformer and Verbraucher.

Gunnar Englund
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
 
Jaxx,

Depending on the size and loading of your new facility, there are numerous voltages available to you. When we design facilities we try to apply the voltages that will provide the most efficient use of power. Where we have industrial facilities, or large campus facilities such as universities or hospitals the loads can be quite large and in some cases lend themselves to using "medium" voltage systems.

These will be anything from 4160/2400V,3ph; 4160/7.2kV, 7.2/12.47kV for some distributed systems which require multiple or distant load points such as a campus with multiple buildings. A new high school here in California can be on as much as 60 Acres of land and have multiple buildings with an aggregate floor area of 300,000 square feet, (over 10000 square meters). We would generally take this as our campus distribution system with local step-down transformers for each building. We would transform down to a building service voltage of 480Y/277V/3PH/4-wire service with Heating, Ventilating and Air Conditioning, (as well as elevators, etc...), at 480V/3ph. Lighting for the most part at 277V/1ph. Then step this down in local electrical rooms to 208Y/120V/3ph/4w local branch circuit panelboards to feed small loads and convenience receptacles, data system power, etc....

Many industrial buildings use medium voltage all the way to the loads, such as 4160 volt/3ph chillers, steel furnaces, and other such large concentrated loads. But for most part, facilites will utilize 480V/3ph for most loads.

What type of industry is your company in? What area of the US are you moving to? Be aware that although we have a "National Electric Code" or "NEC", most areas follow localized versions of this. In California, for example we follow currently the 2004 California Electric Code, (Also known by the State government as State of California, Title 24, Part 3-but you don't need to concern yourself with that part). The 2004 CEC is simply the 2002 NEC with the 2003 California Amendments. Many states will localize the NEC for their particular requirements.

Good luck with your project, I hope you keep us up to speed on it's progress.

Gutes Gluck und Auf Wiedersehen!
 
Thank you guys for your great support!

So it could happen that a company has to get a new tranformer, just because they bought a new machine that works with a different voltage?
In consequence, a company has to have a few different wirings if they have machines with different voltage requirements?

Thanks again

Marc
 
Thank you EEJaime. I didn't refresh the page so I just saw your detailed reply!
 
You are welcome Jaxx.

As for the need for additional transformers to feed specific equipment; it is not uncommon to provide special transformation for some critical piece of equipment. However, many equipment suppliers will have equipment with multiple ratings or adjustable input power capabilities to enable them to work on differing facilities' systems. If a piece of equipment is important enough to utilize in a facility with differing voltages available-then a point-of-use transformer may be an investment worth making.

Regards,

EEJAIME
 
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