Step-up transformer

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  #1  
Old 05-12-03, 09:07 PM
MikeVB
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Step-up transformer

Does anyone know if there exists a step-up transformer to get 220V from a 120V recepticle? If there is one do you know where I can get one online?

I have found step-up transformers online but they are all for running 220V European appliances from 120V North American power sources. What I need is a step-up that will take 120V U.S and step it up to 220V U.S. to run a compressor I bought.

Thanks

Mike
 
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  #2  
Old 05-13-03, 07:02 AM
DaveB.inVa
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Youll be much better off to run a dedicated circuit that is properly sized for this load. If this compressor requires 20 amps at 240v then a 20 amp 120v circuit will simply not do no matter what transformer you use. Even then if it were possible to do as you wish the transformers cost in this application would probably be very cost prohibitive.
 
  #3  
Old 05-13-03, 09:31 AM
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Dave is correct, you can certanly step up the voltage to 220V, but your 120V circuit will probably not have the necessary gauge to supply that current. In which case you'll have to change your 120V circuit to handle your doubled current.
 
  #4  
Old 05-13-03, 05:28 PM
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With such a 2:1 (roughly) step-up transformer, every amp you draw from the 220V (secondary) side will pull 2A from the 120V circuit.
 
  #5  
Old 05-13-03, 06:01 PM
MikeVB
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Thanks everyone.

I guess I should have gave more information in my original post.

This compressor is a 1/2 hp silent compressor and is rated at 2.9 amps @ 220V. With those ratings it will only be drawing a scant 638 watts so there should be no problem running it with a 1,000 watt transformer.

The problem I have found though is that the step-up transformers are designed to step up North American 120V to European 220V I believe. The web site here:
Voltage converters

says under the 'FAQ's' that you cannot run an American 220V dryer off of the transformers because they are designed for single-phase 220V current and American 220V has two 110V circuits to make the 220V.

So I am assuming that these transformers are made for North American to European conversion and will not work for North American only conversion correct?

Mike
 
  #6  
Old 05-13-03, 06:45 PM
DaveB.inVa
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It depends. Your compressor only needs straight 240v so the european setup would work just fine because dryers need both 240v for the elements and 120v for the motor and timer. Your compressor doesnt need 120v at all so the 240v supplied by the transformer would work fine.

Just be sure that this is an actual transformer and not some cheap "converter" because those converters use electronics for their transformation.

I still think it would be better to run a dedicated circuit because a 1 KVA transformer is pretty bulky and costly as well.
 
  #7  
Old 05-13-03, 06:53 PM
MikeVB
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Dave,

Thanks for the reply.

The transformer I was considering was at the link I posted above and sells for under $60.

I don't know if it is an actual transformer or not but it weighs 20 lbs so I am assuming it is. Here is the link to it:

1,000 watt voltage transformer

About that answer you gave me in regards to the American dryer the web site says this in the FAQ's:

Can I connect an American 220 Volt Dryer to a Transformer?


No you cannot connect an American 220 Volt Dryer to a Transformer. Voltage Transformers are made to convert single phase 110 or 220 volt. American 220 volt consists of 2 phase of 110 volt and European 220 volt consists of 1 phase of 220 volt.

Is this different from what you said in regards to a dryer?



Mike
 

Last edited by MikeVB; 05-13-03 at 07:10 PM.
  #8  
Old 05-13-03, 08:24 PM
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It does look like a "real" transformer. There is really no difference between the european 220V and the US 220V when put on a scope (actually the US should be 240V, but generally is lower). They should both look like a nice sine wave.
 
  #9  
Old 05-13-03, 08:32 PM
MikeVB
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Originally posted by trinitro
It does look like a "real" transformer. There is really no difference between the european 220V and the US 220V when put on a scope (actually the US should be 240V, but generally is lower). They should both look like a nice sine wave.
I realize that but does it make a difference in that the European 220V only uses two wires to get the 220V and we use two sets of two wires to get 220V? Would that in essence be creating a dual-phase 220V since there are two sets of single-phase wires?

I am not an electrician so I am having a bit of trouble figuring this out. I took some electronics years ago at a junior college but I never got into what phases do in electric motors.

Mike
 
  #10  
Old 05-13-03, 09:49 PM
DaveB.inVa
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The info your reading is misleading.
We use just 2 wires to get 240v as well.
You cant connect the dryer because the dryer requires 240v PLUS 120v. In other words the 240v is for the heating elements, it is obtained between 2 wires with 240v between them. The timer and motor require 120v, it is obtained between 2 wires with 120v between them.

An American system has 3 wires. 2 hots and a neutral. From one hot to the other hot youll get 240v. From any hot to the neutral youll get 120v.

In a European system you have 2 wires. From one hot to the other youll have 240v.

Your compressor has no requirement at all for 120v, meaning all that compressor motor needs is 240v. Your compressor also only needs 2 wires to operate. If all you get from the transformer is 240v and all your load needs is 240v then you have absolutely no problem. The neutral is NOT essential for proper operation of a straight 240v load.

There is no magic about it at this level. The transformer gives you the required voltage for the equipment. Your not dealing with a dryer.


The transformer will only provide you with 2 wires with 240v between them. The dryer will not work because the transformer doesnt provide the proper tap that supplies 120v to run its timer and motor. A load such as your compressor that doesnt require 120v for operation will work just fine.

If you look on your compressor plug you should see 3 prongs. 2 are the leads to the motor and the third will be the equipment ground. There is not a 4th prong for the 120v load.

This also brings up grounding. With this transformer you are creating a seperatley derived system and it should be grounded accordingly. Make sure that this is taken care of by the manufacturer.
 
  #11  
Old 05-13-03, 10:24 PM
MikeVB
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Thanks Dave.

I appreciate the help.

I think they need to re-word that question as it doesn't make much sense. I am calling them tomorrow to see what they say about the unit being grounded, etc.

Mike
 
  #12  
Old 05-14-03, 06:20 PM
MikeVB
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Dave,

I called the manufacturer today that makes that step-up transformer and asked the person if I could run a 220V compressor off the transformer and he said no. LOL

He said it is specifically made to run European single-phase 220 off of American single-phase 110. I don't think he knows what he is talking about.

When I got home this afternoon I looked at the ratings on the back of the motor of this compressor and it says it is rated for 185-240V and 50Hz! This IS a European motor after all.

Mike
 
  #13  
Old 05-14-03, 06:43 PM
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Why not simply run you 220V compressor off a regula 220V outlet? It will run a bit faster, but it will work just fine.
 
  #14  
Old 05-14-03, 08:13 PM
MikeVB
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trinitro,

That is what I was planning on doing if I had to.

The thing is that I would like it to be portable if possible since it is an airbrush compressor and if I needed to paint something for someone such as a mural on a wall then I would need to be able to bring the compressor. Finding a 220V dryer plug could be difficult in many instances.

Mike
 
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Old 05-14-03, 08:54 PM
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The step up unit should work also, if it's drawing 2.9A at 220V it will draw 5.8A off the 120V line (more actually since the step up Xtrasformer is not 100% efficient). Realistically all you really need is a transformer which will provide you with the necessary number of windings, and can handle your current. Just make sure whatever you get can handle at least 5A at 220V as your motor will try to draw a large amount of power at startup.
 
  #16  
Old 05-15-03, 06:11 AM
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Take a very close look at the motor. Many of them have internal wiring connections to make them run off 110v.
To help clarify the difference between north ammerica and europe think of a center tap transformer. That is the system we use in NA. The center tap is the neutral.
 
  #17  
Old 05-15-03, 08:07 PM
MikeVB
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I contacted one of the top silent compressor techs in the country today and he said that the problem I am really facing is running this 50Hz motor on 60Hz current!
He said it would not last that long on our 60Hz current here in the U.S, although the guy I bought it from said he had another one exactly like it and he ran it for 3 years with no problems.

Mike
 
  #18  
Old 05-15-03, 08:46 PM
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Where did this machine come from?
You bought in the US, correct?
Would there be any chance of changing the motor, and replacing it with a 60Hz motor, either 120 or dual-voltage?
The reason the customerSupport may have said no to running a significant motor off of the converter, may have to do with the internal design of the unit.
I question what these converters were designed for, if not euro. apps. I am inclined to say go ahead with the converter at your own risk.
--> How about warranties, and return policies? ****

gj
 
  #19  
Old 05-15-03, 08:54 PM
MikeVB
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Gj,

Thanks for the reply.

I bought this compressor used from a guy who lives about 90 miles from me. The unit was manufactured in 1991 so the warranty is past. I could change the motor but it is extremely expensive as these Jun-Air compressors are manufactured in Denmark and the motor alone sells for $850 new!

Mike
 
  #20  
Old 05-15-03, 08:59 PM
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I was implying a US motor. How odd is the design of the motor?
Are there other electronic controls that will be affected by changing the voltage?
 
  #21  
Old 05-15-03, 09:03 PM
MikeVB
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I wouldn't even begin to attempt that.

These are oil-filled units with the motor, and piston inside a cast iron head and I highly doubt a U.S. retrofit would work.

Mike
 
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