motor voltage ratings

The standard voltages in the USA include:
240/120 single phase 240 (with 240/120) three phase delta 208Y/120 three phase wye
480Y/277 three phase wye
Yet motor ratings continue to specify voltages of 115, 230, and 460. What's the story with this? Is this just the middle of a range of voltages they can work with (e.g. 220 through 240)? Or are they just hanging on to legacy to avoid confusing the electricians who would be installing them?
I have seen motors rated for 208 volts. There they hit it right on the mark. But I don't see them rated for 240 (just 230).
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     snipped-for-privacy@ipal.net writes:

Well, 230V is the mains voltage adopted by all the CENELEC coutries (all the EU and some other countries which decide to follow the EU). So presumably these motors are also (or maybe primarily) aimed at these countries.
UK did have a 240-0-240 supply which was used on farms if the nearby HV feeder was only single phase. That would now be 230-0-230 officially, but I rather suspect all these supplies would have become 400/230Y over last 30 years or so. Maybe there are some other parts of Europe with 230-0-230?
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| snipped-for-privacy@ipal.net writes: |> The standard voltages in the USA include: |> |> 240/120 single phase |> 240 (with 240/120) three phase delta |> 208Y/120 three phase wye |> 480Y/277 three phase wye |> |> Yet motor ratings continue to specify voltages of 115, 230, and 460. |> What's the story with this? Is this just the middle of a range of |> voltages they can work with (e.g. 220 through 240)? Or are they |> just hanging on to legacy to avoid confusing the electricians who |> would be installing them? |> |> I have seen motors rated for 208 volts. There they hit it right on |> the mark. But I don't see them rated for 240 (just 230). | | Well, 230V is the mains voltage adopted by all the CENELEC coutries | (all the EU and some other countries which decide to follow the EU). | So presumably these motors are also (or maybe primarily) aimed at | these countries.
How long has this been? It appears that the 115/230/460 ratings have been used here for several decades. But certainly it is believable that the rating is given for export compliance. But I don't see any 400 volt motors around (but then, you wouldn't expect them to work in the US since the three phase power is either 208/120 or 240 or 480/277 with 600 in Canada).
| UK did have a 240-0-240 supply which was used on farms if the | nearby HV feeder was only single phase. That would now be 230-0-230 | officially, but I rather suspect all these supplies would have become | 400/230Y over last 30 years or so. Maybe there are some other parts | of Europe with 230-0-230?
I've not been seeing any reports of problems running 230 volt rated motors on 240 volts here in the US. But I have seen first hand problems running such motors on the 208 volts that is present when each leg of three phase power is 120 volts. There are plenty of three phase motors around here for 208 volts. It seems single phase motors for 208 volts are hard to find. Yet sometimes thats the voltage you have to use. And I've seen two motors rated for 230 volts burn up (after about a week of working) on 208 volts.
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IBM never seemed to have a problem. All of our big systems used dual rated 208/240v motors. they ranged from very small fractional HP motors up to over 3 HP.
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|> It seems single phase motors for 208 volts are hard to find | | IBM never seemed to have a problem. All of our big systems used dual rated | 208/240v motors. they ranged from very small fractional HP motors up to over 3 | HP.
And these ran on single phase? Hmmm.
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Most were 3 phase (the object of the exercise) but there were some single phase.
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Greg wrote:

ISTR many were 400Hz too (with MG sets to do the conversion). Many moons ago I designed a phase-rotation detector that was voltage and frequency independent for the 303X series. Fans going backwards wasn't goodness and the "new" phase-controlled regulators lost much magic smoke when wired "only" 120 degrees out. The system was designed to refuse to power on if it was connected to an illigitamite power source.
Back to the point, yes, IBM designed motors and transformers to take anything that could reasonably be handed them. It was cheaper than designing for specific localities. ...and then having them moved to another. MG sets were a normal thing.
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over 3

Yes but ...
When I was in the service the "standard power" was 120/208. The window air conditioned in theory could operate from 208 to 240. BUT a lot of them didn't last long in the tropics.
IOW: one way or another you "pay" when you don't run motors at the right voltage or try to make a "one size fits all" motor.
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|> IBM never seemed to have a problem. All of our big systems used dual rated |> 208/240v motors. they ranged from very small fractional HP motors up to | over 3 |> HP. | | Yes but ... | | When I was in the service the "standard power" was 120/208. The window | air conditioned in theory could operate from 208 to 240. BUT a lot of them | didn't last long in the tropics. | | IOW: one way or another you "pay" when you don't run motors at the right | voltage or try to make a "one size fits all" motor.
I've experienced that myself. One place I used to work expanded the computer room. The A/C people said the existing A/C size was sufficient. But as soon as the Texas summer hit, it didn't take long for the A/C to die. Turns out a motor burned out. So they simply replaced it (they had one in stock). It burned out 2 weeks later. Replaced again. That one burned out. Finally, someone noticed the problem. The whole A/C system was running on single phase and the motor was rated for 230 volts. But due to an electrical conversion several years before for another tenant, three phase was brought in and we were actually getting 208Y/120. I knew we were getting that since I selected the UPS based on that. But I didn't know the A/C units were all on single phase, and now getting only 208 volts. The A/C ran, but our office ran ours to the maximum, which combined with the overcurrent from 208 volts, was the culprit in the burnouts. The A/C guys special ordered a 208 volt single phase motor (rather than rewire everything for three phase) and it didn't burn out thereafter, and the A/C kept things cool (so they really were right that it had the tonnage needed).
Things designed for three phase are surely going to have a lot of 208 volt supplies to deal with, so three phase motors and other stuff for three phase is going to be made for 208 volts (and other voltages as found in the US). But for single phase, 208 volts is much less common. If you have 208 volts you probably have three phase and would choose a three phase A/C (or so the thinking probably goes). So 208 volt single phase motors, while certainly made, would likely not be a common stock item. And you do get people saying (of a 230 volt motor) "It'll work on 208 volts". One might be better off buying 200 volt Japanese motors in such a case.
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phase
volts
the
Maybe, maybe not.
The 120/208 service is kind of silly. The 208 (even in 3 phases) just ain't enough to supply REAL power. And faily efficient single phase motors are availale up to several hp.
Trouble is that (at least about here), the utility is getting away from the 120/240/240 type service (which provided 240 three phase and "regular" 120/240 service) and pushing 120/208 or 240/416. Since the latter requires transformers for "normal" loads and since some stuff isn't rated for more than a certain voltage over ground, a lot of stuff will be expected to work on 208.
It may not be "shipped" with 208 volt motors but there will be plenty of 208 volt REPLACEMENT motors needed it utilities keep shoving 120/208 on their customers.
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| The 120/208 service is kind of silly. The 208 (even in 3 phases) just | ain't enough to supply REAL power. And faily efficient single phase motors | are availale up to several hp. | | Trouble is that (at least about here), the utility is getting away from the | 120/240/240 type service (which provided 240 three phase and "regular" | 120/240 service) and pushing 120/208 or 240/416. Since the latter requires | transformers for "normal" loads and since some stuff isn't rated for more | than a certain voltage over ground, a lot of stuff will be expected to work | on 208.
What utility is pushing 240/416? I've looked at a lot of utility tarrifs and "service guide" publications, but I haven't seen 240/416 available anywhere in the US. I have seen 139/240 available at a couple utilities. 139/240 (240Y/139) would be a reasonable replacement for 240 delta that doesn't have any 120 volt loads on it. And I have seen 240/416 available in generators (especially military surplus).
Personally, I'd like to see a utility offer all of 208Y/120, 240Y/139, 416Y/240, 480Y/277, and 600Y/347. Single phase transformers to make a bank for 416Y/240 are readily available (they are normal 240 volt ones). 240Y/139 would be more of a problem since that would require a split 277/139, and not many of those seem to be around (yet two utilities do offer that voltage).
OTOH, the crazy side of me would like to see the US just switch everything over to 480Y/277 :-)
| It may not be "shipped" with 208 volt motors but there will be plenty of 208 | volt REPLACEMENT motors needed it utilities keep shoving 120/208 on their | customers.
It seems the variety of those 208 volt motors for single phase is still not a commonly stocked item. I can see them being readily available in three phase versions at 208 volts, since there is so much of that.
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writes:

what's with this 380/660 motors ive seen a lot of in the UK recently? Ive been hooking them all up for 380 but don't know how long they will last? Ive asked the manufacturers and have been told they are good to 400v. but I haven't met a sparky yet that's had <415v on a unoverloaded 3ph supply.
sQuick (UK)
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snipped-for-privacy@ipal.net wrote:

It allows for voltage drop. iirc I've seen 200 rated motors for a 208 system.
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No Spam, you're correct. Rated voltage for motors in the US is traditionally 4-5% lower than the corresponding nominal supply voltage: 115V motor/120V supply, 200V motor/208V supply, 230V motor/240V supply, 460V motor/480V supply, 575V motor/600V supply. This difference accounts for voltage drops in the Owner's distribution system.
If you want to investigate further, look at the IEEE Red Book and the National Electrical Code.
Regards, Chris Johnston
wrote:

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wrote:
| No Spam, you're correct. Rated voltage for motors in the US is | traditionally 4-5% lower than the corresponding nominal supply | voltage: | 115V motor/120V supply, | 200V motor/208V supply, | 230V motor/240V supply, | 460V motor/480V supply, | 575V motor/600V supply. | This difference accounts for voltage drops in the Owner's distribution | system.
And can you affirm that it is _not_ for the purpose of matching the 230 volt nominal standard in Europe?
I have seen motors rated for 208 volts but not for 200 volts. It would seem that either the voltage drop margin is not included for these or else they are for markets where the voltage standard is really 220 volts or 216 volts (I found that at least one power company in the US is doing 216Y/125 in network service areas).
I'd be curious to see what the rate motors for in Japan where the nominal is 200 volts (100 line to ground for single phase, 115 line to ground for three phase).
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Phil, I can assure you that these American National Standards Institute (ANSI) voltage standards have been around for a long time, long before the "one size fits all the world" movement that is in vogue. They began early in the last century, when US manufacturers had no interest in selling anything other than products for domestic use. This was during the period when DC and 2-phase AC fell out of fashion as supply voltages and 16 Hz, 25 Hz and 40Hz as supply frequencies.
You are correct in stating that there are 208 volt-rated motors as well as 200V. The 208V-rating is generally used on a motor that is dual-rated for both 208V and 230V.
You are also correct about some utilities supplying voltages that differ slightly from the standards. Another utility provides 460V rather than 480V. Regardless, these utilities are regulated monopolies in most areas and the voltage delivery standards are set by law.
Regards, Chris Johnston On 26 Jun 2004 16:16:49 GMT, snipped-for-privacy@ipal.net wrote:

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On 22 Jun 2004 02:09:02 GMT, snipped-for-privacy@ipal.net wrote:

What you are referring to above are the DISTRIBUTION voltages. Motor voltage ratings are called UTILIZATION voltages. This is to allow for expected voltage drops. Here is an example I just worked on. 480V supply at the substation transformer secondary, but 430V measured at the motor connection box 1200' away (linear measurement) after going through switchgear and MCC. It is still within the tolerable rating for a 460V motor (460V - 10% = 424V). If the motor were truly wound for 480V, the lower tolerable range would be 480-10% = 432V so the motor would draw too much current and / or not provide rated torque. It is a compromise.
208V ratings are a compromise of a compromise. You could safely run a 230V rated motor on 208V supply (230 - 10% = 207), however many 208V systems tend to get overloaded and drop to 200V, still within acceptable tolerance for a 208V system, but out of tolerance for a 230V motor. However it is also OK to run a 208V wound motor at 230V in a pinch (208 + 10% = 236, not great, but doable), hence the existance of 208V rated motors.
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| On 22 Jun 2004 02:09:02 GMT, snipped-for-privacy@ipal.net wrote: | |>The standard voltages in the USA include: |> |>240/120 single phase |>240 (with 240/120) three phase delta |>208Y/120 three phase wye |>480Y/277 three phase wye |> |>Yet motor ratings continue to specify voltages of 115, 230, and 460. |>What's the story with this? Is this just the middle of a range of |>voltages they can work with (e.g. 220 through 240)? Or are they |>just hanging on to legacy to avoid confusing the electricians who |>would be installing them? |> |>I have seen motors rated for 208 volts. There they hit it right on |>the mark. But I don't see them rated for 240 (just 230). | | What you are referring to above are the DISTRIBUTION voltages. Motor | voltage ratings are called UTILIZATION voltages. This is to allow for | expected voltage drops. Here is an example I just worked on. 480V | supply at the substation transformer secondary, but 430V measured at | the motor connection box 1200' away (linear measurement) after going | through switchgear and MCC. It is still within the tolerable rating | for a 460V motor (460V - 10% = 424V). If the motor were truly wound | for 480V, the lower tolerable range would be 480-10% = 432V so the | motor would draw too much current and / or not provide rated torque. | It is a compromise. | | 208V ratings are a compromise of a compromise. You could safely run a | 230V rated motor on 208V supply (230 - 10% = 207), however many 208V | systems tend to get overloaded and drop to 200V, still within | acceptable tolerance for a 208V system, but out of tolerance for a | 230V motor. However it is also OK to run a 208V wound motor at 230V in | a pinch (208 + 10% = 236, not great, but doable), hence the existance | of 208V rated motors.
So the + or - 10% is worked out from 230, so the range would be 207-253, but is a 208 volt motor figuring its 10% from exactly 208 (187.2-228.8)? Or would it do so from a lower voltage? Like 200? If the logic for 230 is to set the range on the low side, then should that same logic be used for 208 and set it at 200?
It would seem to me that nameplate ratings might be clearer if they would specify accept voltage ranges under certain standard usage duty and start cycle ratings.
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