American voltage level

[68709359]

Hi All,
I am invloving one project which which employ american voltage level. As far as I know, american has the following voltage type(60Hz):
120/208V for lighting and outlet, solid earthed
240/416V for ? solid earthed
277/480V for LV such as motor, solid earthed
2425/4200V for MV load, low resistance earthed
the Higher voltage ?

Could anyguys help me to confirm whether it is right and detail it? what type of consumer will use which voltage?
In general, what's standard transformer type?

thanks in advance

 

[wareagle]

I don't think you will find 240/416 voltage. Most large commercial and industrial will be 277/480 wye. You may be able to get 480 volt delta. It would be up to the utility.
MV is 2400/4160 for larger industrial. You may also have 7.2/12.4 kv and 7.6/13 kv both delta wye.

 

[alehman]

120/208 and 277/480 (solidly earthed) are by far the most common 3-phase voltages. Motors for these voltages are typically rated 200 and 460, respectively.

There is more variety at medium voltage. 2400/4160, 6350/11000, 6900/12000, 7200/12470, 7620/13200, 7970/13800, 14400/25000, 19900/34500 are all in use.

Essentially all power is 60Hz.

 

[jraef]

It's not quite that simple. We are a very diverse lot.
Low voltage 3 phase:
200Y115V
208Y120V
230V delta
240V corner grounded delta
240/120V reg leg delta
480Y277V
480V corner grounded delta
Some 600V delta here and there
Some 25Hz here and there as well
Most dual voltage motors are 460/230 wound
No such thing as 240/416V

MV: Click here

No such thing as a "standard transformer type". Every utility can do what they want depending on their geography, legacy, demographics etc., and most do.




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[68709359]

Thanks for All,
Your reply make me more clear than before, but I am still lost about delta for LV. In general, for single phase load, we use three wire(phase,neutral,ground); for three phase load motor/ feeder, we use four/five wire(3phase,ground/3phase,neutral,ground). How do we solve the protection wire problem?

In addition, as alehman said, for a new project, 120/208V 277/480V is common and simple for LV, but what's for HV similar as 6/10KV widely in Europe or China.

 

[68709359]

ALL,
I also want to know the range for 480V, is it +/-5%? what's for MV level?

 

[Skogsgurra]

A funny thing is that one of the information panels at the Hoover dam says that "Before being used in the home, the voltage must be reduced to 240 volts".

So most americans that learned about electricity there think that 240 V is the standard voltage in the USA.

Wonder if that panel was made in England, before they changed to 230 V?


I have taken a fotograph of that text and can mail it to anyone interested.

Gunnar Englund

http://www.gke.org

 

[itsmoked]

That's great... A guy has to come from Sweden to discover an error on a placard in our "greatest" dam.

 

[stevenal]

No error. Folks are confusing utilization voltage with service voltage. 240 is what's being delivered to the service entrance so downstream equipment will see a delivery of 230. Same with the others. For all the nominal voltages and their tolerances, see ANSI 84.1. The range A tolerance for a 480 service is 456 to 504. For a 460 utilization, it is 440 to 500. Range B is wider with the expectation that excursions outside range A into B are infrequent.

 

[SomeYahoo]

This is great fodder for a FAQ. Would be great to get a colaboration of world voltages in one place. I know I find myself searching for the information frequently.

Just a thought...

 

[dpc]

thread238-71901

This question comes up fairly often. There are several old threads on the subject.

I think we like to make it seem more confusing that it actually is. As stevenal mentioned, the main source of confusion is the difference between nominal delivery voltage (e.g. 120V) and utilization voltage (115V or 110V).

 

[alehman]

240 3ph is always delta connected and can be ungrounded, corner grounded or with a center tap on one leg grounded. 240 3ph is typically found in older buildings and rural settings.

480 3ph can be Y solidly grounded, Y resistance grounded, delta corner grounded or Y or delta ungrounded. Y solidly grounded is by far the most common. 480 has become somewhat of a defacto standard for industrial and larger commerical use for new installations.

The service voltage tolerance is +-10%.

 

[Skogsgurra]

I stand corrected. zdas04 just told me (over a couple of beers in Farmington) that there are 2x120 V systems. So it would be correct in a way to say that you have 240 volts in your houses. But not available in wall sockets, I think.

Gunnar Englund

http://www.gke.org

 

[jraef]

Correct Gunnar.
Wall sockets, at least in living spaces, are 120V only, usually 15A, but occasionally 20A. We typically have 240V sockets for large appliances and sometimes in the garage or workshop for bench power tools. In college I used to sell power tools at Sears. You would be surprised at how many people brought in portable 120V tools burned out from plugging them into 240V sockets. They have different pin configurations, but the real dunces figured out how to cut the plugs off and put on one that fit, trying to get "more power" out of their saw or drill. They probably did for a few seconds!

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[jraef]

This is great fodder for a FAQ. Would be great to get a colaboration of world voltages in one place. I know I find myself searching for the information frequently.

I find myself looking for it often as well. I have found sites in the past, but I lose track of them and Google is too general now, I get 10,000 hits and none of them are what I want. I'd be willing to start the FAQ, but it needs to be a true colaborative effort. After I start it, people in different parts of the world can send me comments (there is a link below each FAQ for comments to the author) and tell me what the voltage standards are in your area, then I'll edit them in. Official and defacto standards should be differentiated if that is pertinent. There seem to be a lot of sites discussing residential and control voltages, so I think we should make this about industrial voltages, including MV.


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[advidana]

Search no more jraef-Try the U.S. Department of Commerce, Bureau of Industrial Economics. Get from them a booklet called "Electric Current Abroad". It is 85 pages and shows all major countries except USA.

 

[jraef]

Well, I saw that too late. I already started the FAQ!
faq238-1168
If that booklet is readilly available and accurate, I can always abandon the FAQ idea.

Thanks for the info advidana, I'll check it out.

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[68709359]

Thanks again for ALL,
Now I have a thought as follows, pls check it!
For a new project,we general use 480/277v level for main LV to provide power for motor or large consumer, and need to install 480/240v center tap grounded transformer to provide 120/240v power to lighting or outlet as some light need 240v.
In addition, I check the ANSI C84.1 and find, the service voltage is about +/-5% for limit A and +/-8.33% for limit B, the utilization voltage is about -10%/+5% for limit A and -13%/+5.833%. the range is right?
And what is for the MV or HV? 3%?

 

[jraef]

The only thing I would change would be the lower voltage system. 120/208V is a little better because you can balance the loads better than with 120/240 center tap. That is only used when the percentage of 120V loads is very small compared to the 240V loads. Most lighting can be accommodated by the 277V connection at the 480V side, and others can easilly take 208V instead of 240 most of the time.

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[stevenal]

Skogsgurra,

I thought you were referring to the 240/230 service versus utilization voltage. General purpose receptacles are 120. Most homes will have dedicated receptacles for dryers and stoves that are 240/120. Other 240 loads like furnaces and water heaters are wired in.