250 volts to 220 volts

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Old 02-14-15, 12:22 PM
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250 volts to 220 volts

Hello,

for our company, we just purchased an industrial CNC machine built in China. We had it built for 220 volts, 2 phase, as we were told that is what we have in our warehouse. Now, when we got it and adjusted all the plugs to fit US sockets, we found out the the voltage in the sockets are from 242v - 249v (mostly in the evening). We contacted the manufacturer and he confirmed that machine should not have problems with 240 volts, but it would be better to keep it lower than that. So 249v might be a big problem for us.

Is there some easy transformer solution to step down from 240-250 to 220 volts?

Thank you very much, please be aware that I do not know much about electricity, volts amps etc )
 
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Old 02-14-15, 12:27 PM
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Is it truly "2 phase", or is it single phase 240 volt. We don't have 220 volts in the USA.
 
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Old 02-14-15, 12:38 PM
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Anyone ever heard of two phase? (A real question from a non electrician)
Single and three phase is the norm.
Far more common to see three phase in an industrial setting.
Any reason you have not contacted a real local electrician?
 
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Old 02-14-15, 01:05 PM
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I would talk to the manufacturer again. Whoever built this machine (even in China) knows the U.S. runs on 240V.
I seriously doubt if they would send you an expensive machine based on 220 only.

Many people in the U.S. learned to call electric 110/220 way back. It's still called that to many and they are corrected here every day.
 
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Old 02-14-15, 01:07 PM
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And if the shop has 3-phase your voltage may be 208 volts.
 
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Old 02-14-15, 02:55 PM
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It is a 2 phase (2 hots). I know there is no 220v in US now, it just confused me when everyone talked about 220ty and it's actually 240ty.

Handyone: Well they said, it can handle 240 volts, but today I measured 249 volts in the socket.

Is there a easy way how to decrease the volts or is it for major wiring upgrade?
 
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Old 02-14-15, 03:03 PM
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Two hot's does not mean it's 2 phase.
Single phase uses 2 hot's and a neutral.
 
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Old 02-14-15, 03:15 PM
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Single phase 240 volts requires no neutral, unless there are electronics or clocks in the device. It is single phase, not two phase. The voltage can be tweaked by the POCO, but 9 volts is not a deal breaker on the machinery.
 
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Old 02-14-15, 03:51 PM
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Is it 60Hz? 220 voltage equipment is often intended for countries with 50hz power.
 
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Old 02-14-15, 04:18 PM
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Two conductors, whether both hots or hot and neutral, supplying an appliance of any kind is a single phase supply regardless of the kind of system supplying the power.
 
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Old 02-14-15, 04:48 PM
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249 is within specifications for 240 volt power.
 
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Old 02-14-15, 05:36 PM
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We had it built for 220 volts, 2 phase, as we were told that is what we have in our warehouse.
Why would you ordsr and expensive peice of equipment without verifying the voltage youo have available? Regardless, what is the service voltage coming into the warehouse? Do you have any stepdown transformers in the building? Maybe all you need to do is adjust some taps.

2 hots doesn't mean 2 phase. It would have to be single phase or 3-phase. You need to get someone qualified in there to tell you exactly what you have and to compare it to the machine specifications before you make another very expensive mistake.

The 2 hots you measured could also be from a 3-phase delta service.
 

Last edited by stickshift; 02-20-15 at 02:52 PM. Reason: corrected typo
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Old 02-14-15, 05:38 PM
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dono

well it has four 2phase vacuum motors, I believe it would not turn them if it was just single phase, right?

it is 50/60hz

so how hard is to get it to 220v, what is needed, is that a major upgrade and what would be the approx costs?
 
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Old 02-14-15, 05:44 PM
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Babajaga..... you NEED to get an electrician in there. Two phase power is very rare and just about extinct.

Your equipment can also not be 50hz or 60 hz...... it's one or the other and it does make a difference.

99.99% of equipment runs on single or three phase.
 
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Old 02-14-15, 06:10 PM
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you NEED to get an electrician in there. Two phase power is very rare and just about extinct.
I think he needs to get a good engineer in there. This is looking like a pretty expensive mistake.
 
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Old 02-14-15, 06:56 PM
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babajaga

What type of "machine" is this ? What is its use and what does it do

Mick99
 
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Old 02-14-15, 07:10 PM
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He wrote it was a CNC machine. Numerical control - Wikipedia, the free encyclopedia
 
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Old 02-14-15, 07:18 PM
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We had it built for 220 volts, 2 phase
The scarey question not answered is did they actually build it for 2-phase. Unlikely but who knows. Not counting grounds how many wires, two or three or four? Three or four not counting ground it could be two phase, especially four wires not counting ground. (Three wires not counting ground more likely would be three phase but could be either.)
 
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Old 02-14-15, 09:20 PM
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Voltage is nominal, kind of like a 2x4. In most cases when a voltage is specced on a nameplate, or by a manufacture, it will be +/-10%. So the manufacture says 240 volts is OK, your 249 volts will be just fine. Voltage will go up and down depending load and time of day in your building. If you really want you can buck the voltage down with a buck/boost transformer, however it is likely unnecessary.

I have wired some equipment that was marked "two phase". In each case what they (the over seas manufacture) meant was two hots, and perhaps a neutral, if required. This can be from a single phase service (one coil in a transformer) or two hots of a three phase service (3 coils) Just make sure that if you have a high leg service and the the CNC requires a neutral that you do not use one of the high legs. You will smoke your CNC for sure.

Side note: I have seen many pieces of equipment that are duel rated for 50 or 60 hz power.

Lastly if this is a commercial installation this will likely be required to be wired by a licensed electrical contractor.
 
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Old 02-15-15, 05:29 AM
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I highly doubt this company custom manufactures equipment for unusual electrical setups. I'm sure the choice was single phase or 3 phase.
 
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Old 02-15-15, 07:02 AM
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Can one of the electricians confirm whether a slight over-voltage ~10-15% on motors is typically a bad thing? Assuming the electronics have switching/regulating power supplies, would the over-voltage typically affect the long-term reliability of the motors?
 
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Old 02-15-15, 07:15 AM
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Voltage within +/-10% will not harm most electrical equipment. Over voltage is better then under voltage for a motor.
 
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Old 02-15-15, 10:27 AM
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So you talked with the manufacturer and they said that it was OK with 240 volts. Why not talk with them again and ask if there are any issues with 249 volts?
 
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Old 02-15-15, 10:52 AM
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And while talking to them ask them if they really specially built it or if they just pulled a standard unit off the shelf. If standard what countries was intended to be used in?
 
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Old 02-15-15, 02:04 PM
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2phase

OK I just talked to electrician, he says in US you call it 220 single phase, although it is called 2 phase anywhere else in the world. He also suggested to buy some step down transformer. Can you guys recommend one? It should be 250 to 220v and at least 50 amps
 
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Old 02-15-15, 02:50 PM
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Electrician is wrong on at least two things. Single phase is called single phase or maybe split phase regardless of the country. A knowledgeable person does not call it 220 volts. Actually it would be a buck bost transformer. I'd call the manufacturer first then get a better educated electrician. Bottom line you can probably just plug it in. No rewiring or transformer required.
 
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Old 02-15-15, 02:57 PM
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I imagine you talked to an electrician in China? Since he said "in US you call it 220 single phase, although it is called 2 phase anywhere else in the world".
 
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Old 02-15-15, 03:12 PM
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Hopefully this was not an expensive mistake and is just a lack of knowledge and correct terminology.
 
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Old 02-15-15, 03:56 PM
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What is the name of the manufacturer?
 
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Old 02-15-15, 07:11 PM
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A knowledgeable person does not call it 220 volts.
There is still plenty of guys out there that are old school and still call it 220, 460, or 110 volts. They will also call receptacles "outlets". It is more of a kind of slang.

Ray is correct. If you wanted to drop the voltage all you need is a buck boost transformer, and with a single phase load you only need one. Although IMO I doubt you do need one, but if the manufacture says you need to drop the voltage, it would be best to do so to preserve the warranty.

Here is a calculator to size a buck/boost transformer: Buck and Boost Transformer Calculator - Schneider Electric United States
 
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Old 02-15-15, 08:39 PM
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We still haven't cleared up if it is 50hz or 60hz.
adjusted all the plugs to fit US sockets,
Which indicates it was not built for North America. That makes it questionable if it is 60hz. If there are any motors that could be a serious problem.
 
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Old 02-15-15, 08:45 PM
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The real fault is the manufacturer. He should have told you the specs you gave him were wrong for the U.S. 2-phase should have been a red flag even if 220v wasn't. Assuming it wasn't made for the U.S.I'd go back to the manufacturer. Maybe we will let you swap it for one made for the U.S.
 
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Old 02-16-15, 10:10 AM
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It all boils down to the wrong equipment was ordered based upon information from an unqualified source.

We had it built for 220 volts, 2 phase, as we were told that is what we have in our warehouse.
 
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Old 02-16-15, 11:10 AM
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I would say there's a good 98% chance that this CNC machine will work just fine in your warehouse. In the US voltages between 220 and 250 all refer to the same thing. I would be really surprised if this machine was designed to operate in such a tight tolerance around 220V instead of simply being built out of commodity parts which are designed to operate in the 220-250 range. You are also likely measuring the voltage on the service with no loads attached. When the motor(s) kick on, the voltage will probably come down to right around 240V. The power company intentionally sets it a little high to compensate for the drop when the load kicks on.

From a practical point of view there really isn't any such thing as two phase, and whomever built this CNC machine wouldn't have any source of motors, controllers and sensors to deal with such a beast. It is much more likely they assumed you meant a standard single phase 240V North American service and built the CNC as such.
 
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Old 02-16-15, 12:35 PM
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A smoke test is probably the next thing you should do.
 
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Old 02-16-15, 01:55 PM
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I'm guessing that I am the only one left here that has actually worked with two-phase systems. Two-phase is either FOUR hot wires or four hot wires plus a neutral in the case of a dual voltage system.

If this piece of machinery has TWO hot wires then it is single phase. If it has three hot wires then it is three phase. Either single or three phase MAY have a neutral wire IF the machine requires dual voltage but that is highly unlikely. There should always be an equipment grounding wire.
 
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Old 02-16-15, 03:13 PM
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I agree 100% with everything that Ibpooks posted.
 
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Old 02-20-15, 02:34 PM
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what transformer type should I use? machine is 7000w, uses around 42 amps (50amp breaker)

could it be this one or what parameters should I look for?

Acme T 1 81048 100 VA Buck Boost Transformer 100 Watt New | eBay
 
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Old 02-20-15, 02:56 PM
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You really need to contact the manufacturer to clarify the items that have already been asked. The transformer might not even be needed.
 
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Old 02-20-15, 02:58 PM
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FWIW, I think a machine consistently drawing 42 amps would need to be on a 60 amp breaker.

Pros - am I wrong?
 
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