280V motor on 230V circuit

| Just a bitch that we have dealt with before: | | Phil- please realize that 207.846096....... is meaningless except that it is
| "about 208". 208V is correct to 3 significant figures which is actually | better than one can assume to be true in practice. If the voltage line to | neutral is actually 120.V (note the decimal) then we have 3 significant | digits implying something between 119.5 Vand 120.5.V | Then all you can truly claim is 208.V | If it is 120.0V then there is reason to assume 208.0 V but no more decimals | than that. | If you have a meter which gives you 120.000000V with less than 1 part in 120 | million error then you can claim 207.846097V for line to line voltage Do | you have such a meter? | | Engineering and physics students who ignore the principle of "significant | digits" lose marks for this "decimal inflation". | | Sure- you can let the calculator carry the extra digits (as it will do | internally) but accepting these as gospel truth to the limit of the | calculator or computer display is simply not on as you can't get better | accuracy from a calculation than the accuracy of the original data (actually | you will lose a bit). All that you get rid of is round off errors in | calculations. | | Since, as you say, precise voltage is not really practical, then | multi-decimal point numbers are meaningless. If we say 120V +/-10% then we | are talking about 108-132V which for line to line becomes 187-229V (average | 208V) and any extra decimal points don't mean anything.
You didn't notice the :-) I put on the number?
We've been over this. I know the practice of significant digits, and how the voltages are designated (two different reasons you can get 208). I do follow the practice of carrying exactly the result of calculations into other calculations. I also use over significance in comparison of numbers.
But I also know that rounding is a form of noise. So I avoid it until the time I end up with the final result. So if I multiply 120 by the square root of three I do get a number like 207.84609690826527522329356 which is either carried as-is into the next calculation, or rounded if it is the final answer. If some other strange calculation happens to give me the value 207.84609690826527522329356 then I know it is effectively equivalent to 120 times the square root of three in some way. But if what I get is 208.455732193971783228 then I know it has nothing to do with 120 times the square root of three, even though it, too, would end up as 208 if rounded to 3 significant digits.
When it comes to _measured_ amounts, as opposed to synthetic ones, then the significance rules dictate how to round the results. With synthetic numbers (e.g. numbers I can just pick), I can also pick the rounding rules for the final results. But if I don't know that the calculations are done (e.g. I am not merely giving a designation for a voltage system), where someone else may take those numbers and do more calculations and round the results, then I do use more significance. But that is no different to me than just carrying that number from one calculation stage to another.
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----------------------------
wrote:

------------------------- Fair enough- but still overkill. For the bulk of the calculations that one does, single precision is more than adequate. Anything more, even for comparison of numbers is really fluff. I simply set my display to show the desired sig figs and let the calculator deal with the rest in its normal internal mode. I don't want to see the extra digits, or , if I do, 1 or 2 is sufficient. Ditto with the computer. Only if I am dealing with ill conditioned sets of simultaneous equations , will I really require double precision.
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snipped-for-privacy@ipal.net writes:

Yes.
It seems they are moving to 400V as well, but I know many Norwegians are paying a hefty premium on their three phase equipment, like heatpumps.
My heatpump use an internally star configured 3x400V compressor, and it would have been easy to wire it for 3x230V if they had brought out all the leads.
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| snipped-for-privacy@ipal.net writes: |
|> |> | Residential power in Norway is normally 230V three phase btw, instead |> | of 400V three phase. Their 230V outlets are two phase and ground |> | instead of one phase, neutral and ground. Their three phase outlets |> | therefore are blue instead of red and have four prongs instead of five. |> |> Is this the system where the voltage is 133 volts relative to ground and 230 |> volts between phases (and formerly 127 volts relative to ground and 220 volts |> between phases)? | | Yes. | |> |> If they still use that system, then I'm interested in buying a UPS designed |> for that. But it is my understanding it is phased out in cities and hard to |> find anymore in rural locations. | | It seems they are moving to 400V as well, but I know many Norwegians | are paying a hefty premium on their three phase equipment, like | heatpumps. | | My heatpump use an internally star configured 3x400V compressor, and | it would have been easy to wire it for 3x230V if they had brought out | all the leads.
If all 6 leads of the 3 windings are brought out separate, then it can be wired in star for 400/230 volt systems, and in delta for 230/133 volt systems. But for Europe in general there would be little reason to do that. There is also no reason to do that in North America, as we don't have any 360/208 volt systems at all.
If I were in Europe I'd rather than the 400/230 volt system. In North America I'd rather have the 480/277 volt system.
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snipped-for-privacy@ipal.net writes:

It would allow the Norwegians to buy less expensive heatpumps from Sweden :-)
It seems like a very simple and cheap thing to do.
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| snipped-for-privacy@ipal.net writes: |
|> |
|> |> |> |> | Residential power in Norway is normally 230V three phase btw, instead |> |> | of 400V three phase. Their 230V outlets are two phase and ground |> |> | instead of one phase, neutral and ground. Their three phase outlets |> |> | therefore are blue instead of red and have four prongs instead of five. |> |> |> |> Is this the system where the voltage is 133 volts relative to ground and 230 |> |> volts between phases (and formerly 127 volts relative to ground and 220 volts |> |> between phases)? |> | |> | Yes. |> | |> |> |> |> If they still use that system, then I'm interested in buying a UPS designed |> |> for that. But it is my understanding it is phased out in cities and hard to |> |> find anymore in rural locations. |> | |> | It seems they are moving to 400V as well, but I know many Norwegians |> | are paying a hefty premium on their three phase equipment, like |> | heatpumps. |> | |> | My heatpump use an internally star configured 3x400V compressor, and |> | it would have been easy to wire it for 3x230V if they had brought out |> | all the leads. |> |> If all 6 leads of the 3 windings are brought out separate, then it can be wired |> in star for 400/230 volt systems, and in delta for 230/133 volt systems. But |> for Europe in general there would be little reason to do that. There is also |> no reason to do that in North America, as we don't have any 360/208 volt systems |> at all. | | It would allow the Norwegians to buy less expensive heatpumps from Sweden :-) | | It seems like a very simple and cheap thing to do.
My guess is that in the cities, they have already changed over to a 400/230 system, or at least a 380/220 system that hasn't been voltage adjusted, yet. What I've heard is the 220/127 system was a leftover in some rural areas of Norway, and also in Spain. Apparently Suadi Arabia has this system so they can make use of both European and American single phase appliances. Mexico also has 220/127 but primarily uses the 127 volt connection (and it's 60 Hz). The really strange thing is Brazil has 220 volts all around the country, with 60 Hz in some parts and 50 Hz in others, and used to use the American 120 volt 2-blade outlet/plug with 220 volts (you can be in for a surprise with that).
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wrote:

There should be no problem with the frequency, the local US base (In Gournes-decomissioned after the end of the Cold War) used a regular 15 kV, 50 Hz feed, from the cretan grid, which was stepped down to 4150 volts and then to 120/240. All with US switchgear and tranformers! (NB for US guys.#10 wire gauge->10 mm2 main feed of residence, #12 ->6 mm2 stove,#14->4 mm2 water heaters, #16->2.5 mm2 washing machines, dryers, #18->1.5 mm2 lighting.-approximately). I think that the personnel of the base used standard US fluorescent light fixtures and other equipment, sone of it was left as some of the buildings "inherited" by the greek state, were converted by us to 230/400 volts, with regular Schuko receptacles.
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snipped-for-privacy@ipal.net writes:

The Philippines uses 220V 60Hz with US-style 2 blade outlets as well.
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wrote:

Misreading of 208V undoubtably, 208 is very common in commercial buildings, that and 277.
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| |
| wrote: |>> |>>>Deodiaus wrote: |>>> |>>>>I have a broken pool motor [magnetek y56y] which will cost a bundle to |>>>>fix |>>>>or repair. |>>>>While doing a search on the web, I found the same model (really cheap) |>>>>but |>>>>wired for 280V, instead of the 230 V load that my wiring is supplies. |>>>>Now, I was thinking of buying the cheap 280V model and installing it |>>>>instead. Aside from rotating at a different speed and |>>>>maybe some power inefficiencies, are there any other drawbacks of |>>>>using the 280V model |>>>>instead? |>>> |>>> are you sure it isn't 208 ? |>>> |>>>--http://webpages.charter.net/jamie_5 " |>> |>> |>> I'd be suspicious that the 280V was a misreading somehow of 230V. |> that sounds more plausible. |> |> | | | Misreading of 208V undoubtably, 208 is very common in commercial buildings, | that and 277.
And where you have 277 you almost certainly have 480. But I suppose it is possible to have 277 alone (is better to use than 120 for lots of fluorescent lighting) or maybe even a 554/277 Edison style single phase split system, where three phase distribution is not available and the higher voltage is desirable for large areas of commercial lighting.
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wrote:

yeah, where do you find 280 volts? it's either 208 or 230.
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Deodiaus wrote:

280vac is an odd rating, so it 230. 120/240 is standard single phase ratings. 208 is three phase. If it's 208 don't get it.
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If you are in North America, and have 120 VAC to the outlets, what you call 220 or 230 VAC in your home is actually 208 VAC, unless you installed some kind of transformer to compensate.
I somehow think that the vendor of the motor made an error. Having 280 VAC sounds to me very unconventional, unless this was some kind of special installation.
I would buy the motor. If in the even that it needed a higher voltage because it lacks torque for your application, then there is the possibility of needed an transformer. This would be expensive.
Some motors have a cover plate inside with strappings, to allow changing its operating voltage, RPM, and direction of rotation.
If you were to run a synchronous motor on a lower voltage, it will have lower torque rather than lower RPM, unless the supply voltage was reduced to below the motor's stable operating threshold. Synchronous motors are dependent on the AC frequency (Hz) for their RPM.
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No, that's not true. It's 240V, the transformer has a grounded center tap so 120 from either side to neutral, and 240 between the hots. You find 208V in commercial buildings and some apartment complexes that are fed with 3 phase, but not in a house, unless you're one of the few lucky people to have 3 phase available.

It's clearly a typo and should be 208V.
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If it's not a silly question, with the motor in question being offered "on the web, really cheap", then if it's e-bay, why not use the 'ask the seller a question' option, or if it's a reseller, use his on-site 'contact us' facility ? Then there would be no debate about typos and exotic voltage issues ... :-)
Arfa
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| If you are in North America, and have 120 VAC to the outlets, what you | call 220 or 230 VAC in your home is actually 208 VAC, unless you | installed some kind of transformer to compensate.
That's only true if the source transformer is a three phase WYE/star type. If you have center tapped delta three phase, or single phase Edison split, then you have genuine 240 volts (although with that delta you may also have a third wire that is 208 volts relative to ground/neutral).
| I somehow think that the vendor of the motor made an error. Having 280 | VAC sounds to me very unconventional, unless this was some kind of | special installation.
It may be a reference to working on 277 volts, which is an available voltage in some large commercial/industrial locations.
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Yes-it could be toast in a couple of seconds. While motors with brushes, like the ones used in short duty appliances, like drills and blenters, will rotate slower in lower voltages, without problems, Asynchronous motors (brushless) will really smoke to death if used in voltages significantly lower than nominal. Can't you find a generic pool motor, if you know the horsepower, voltage (3 phase? line to line) and intake and outlet gauge? and maybe rpm?
HTH,
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