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from the Engineering department...
What is the Standard 3-phase voltage supply in the US
Engineering and workplace issues. topic
Posted by SSteele on 1 September, 2001 - 11:04 am
Standard voltages - What is standard? I am trying to determine a standard for design, and I notice that industrial companies throughout the US use the following 3-phase voltages; 208, 220, 230 440, 460, 480, etc; Canada using 575VAC. Even if you consider +/-10% of nominal voltage, conditions exist in which voltages may be too high for supply to a machine. If a 3-ph Isolation transformer is used with 5% taps, I've just added greater cost and another enclosure to my small workcell. Is the common nominal voltage supply "creeping" upward from 440VAC 3-ph to 460, 480, etc. just as the nominal "120VAC" 1-ph did? (110VAC to 115VAC to 120VAC; Or maybe I am completely "off-my-rocker" associating the two...)
I am looking only for references to a standard indicating typical/nominal values, or replys from individuals with some time spent in industrial design.


Posted by Larry L on 2 September, 2001 - 1:05 pm
In My experience (16 years in industry) the standard is 480volts. I consider 460V to be the same and even 440V is within the 10% rule. With a good supply the voltage will stay between475V and 481V. In some areas you will find mucjh greater dips and sensitive equipment will need a constan voltage transformer. Many industrial settings also make extensive use of variable frequency drives which can generate alot of noise on power lines in the plant but that is another subject.


Posted by John Waalkes on 4 September, 2001 - 12:58 pm
Agreed, but don't forget "light industrial", those guys with the small shops and 208/120 volt systems.

While they will never come close to the big plants in size, they do make up (at least some of it) in volume.


That would be a good question to ask a drives sales rep, what's the percentage of each that they sell?

As an aside, we're building a testbed for a local university which will simulate one of our vertical lifts. When I told our electrican that we needed a 208 3ph drive he looked at me like my head fell off.

He didn't know that they made such a thing...

I guess that it comes from working a sheltered career :)


John


Posted by Jeffrey Eggenberger on 4 September, 2001 - 2:08 pm
440 is the same as 460 or 480 in the same way as 110 is the same as 125. 220 is different from 208 however. The voltage should not "creep" on a
particular machine.

There is no such thing as a natural-born pilot. Chuck Yeager

Jeff Eggenberger


Posted by Michael Griffin on 5 September, 2001 - 4:37 pm
At 13:36 01/09/01 -0400, SSteele wrote:
<clip>
>Standard voltages - What is standard? I am trying to determine a standard
>for design, and I notice that industrial companies throughout the US use
>the following 3-phase voltages; 208, 220, 230 440, 460, 480, etc; Canada
>using 575VAC. Even if you consider +/-10% of nominal voltage, conditions
>exist in which voltages may be too high for supply to a machine. If a 3-ph
>Isolation transformer is used with 5% taps, I've just added greater cost
>and another enclosure to my small workcell. Is the common nominal voltage
>supply "creeping" upward from 440VAC 3-ph to 460, 480, etc. just as the
>nominal "120VAC" 1-ph did? (110VAC to 115VAC to 120VAC; Or maybe I am
>completely "off-my-rocker" associating the two...)
>I am looking only for references to a standard indicating typical/nominal
>values, or replys from individuals with some time spent in industrial
>design.
<clip>

You mentioned that "Canada using 575VAC". Actually, 600VAC is much more common in Canada than 575. I believe that 575 is gradually disappearing in favour of 600. If you are planning on designing something for use in
Canada, you would be better to use 600VAC. We also use 208 (since it is related to 120VAC via a 'Y' connection), but this is typically derived from a local transformer connected to the 600V bus.

I am less certain as to what is used in the US, but I believe that 480 and 440 are the most common, plus of course they also use 208 due to the relationship to 120. An American could probably give you a better idea of the correct proportions for the various voltages.

In either case, I don't think there is any general trend to "creep upward". It is just that all the voltages you mentioned were found at the same time in different places. What has been happening is that some voltages are dissappearing by a slow process of standardisation. A similar process occured with frequency. For example, only a very few industries in Ontario still use 25 Hz (and even they may have dissappeared recently).

If you are attempting to design a standard machine for sale, your question should perhaps not be "what are the most common voltages?", but rather "what are the most common bus voltages?". It may be that not all of the voltages you have mentioned are commonly distributed via the plant's main bus. In addition, some voltages may more common in particular industries or in older plants.

Most builders of standard machines seem to solve this problem by either:
a) Using a transformer with multiple primary taps, or
b) By installing a transformer with the appropriate voltage for the particular customer in question, or
c) Requiring the customer to supply their own transformer if necessary.

The most appropriate option depends upon how big of a transformer you need and what sort of load you are powering.
Your e-mail address seems to indicate that you work for Schmidt Presses. I am only familiar with them as manufacturers of small pneumatic assembly presses which would not seem to consume much power. What size of load do you actually have, and what are its characteristics? That is, are they simple motor loads or do you have high impulse loads such as half-cycle
resistance welders?

**********************
Michael Griffin
London, Ont. Canada
**********************


Posted by David Paden on 3 October, 2001 - 11:06 am
Here in the US, the transformer is normally rated higher than the motor (or load) to allow for voltage drops. The transformer secondary is usually 480 (or 240 or 208) and the motors are rated 460, 230 or 200 volts. 480 and 460 are considered the same. There are some industeries in the US that use 600 volts at transformer and 575 volt motors. The above covers most 3 phase usage in the US. There has been voltage creep over the years - in the 1930s and 40s (maybe even 50s)the transformers were rated 460 (or 230 volts) and the motors were rated 440 and 220 volts. Mostly, you only see the lower voltages on very old systems. That also extended to medium voltages - what is now 2400 volts was 2300 volts in the old days and motors were rated 2200 volts but now are rated 2300 volts.

David


Posted by Tom on 5 February, 2002 - 5:24 pm
David:

Which industries in U.S. use 575/600V. And, if you know, why? Thanks
Tom


Posted by James on 1 March, 2002 - 3:03 pm
575 volt is seen is some areas in the Northeast and Southeast, primarily Georgia. The primiary industries that required this was textile factories. Standard voltage for the US is 208-230/460. You will of course see request for 440 or 480 volt.


Posted by jimmy kwe on 11 March, 2014 - 5:08 am
Sir, if may i know, what a standard medium voltage in usa?
It's same like europe? 3kv/3,3kv...

Or 2.4kv?

Tq
Jimmy kwe


Posted by Bill Schwarz on 11 March, 2014 - 1:24 pm
ANSI/IEEE Standard 141 (red book) specifies standard nominal system voltages. These also appear in ANSI standard C84.1. For medium voltage, there are numerous standard voltages, starting at 2400V, 4160V, and up to 69,000V.


Posted by Bob Peterson on 11 March, 2014 - 8:22 pm
4160 is pretty common.

--
Bob
http://ilbob.blogspot.com/


Posted by Joe E. on 12 March, 2014 - 12:44 pm
Our utility feeds us 12,470V, which we then step down to 480V.

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