Supply 1 Phase Motor

If output of transformer is 220 phase to phase then you definitely connect the motor with two phase.

Go for it, phase to phase

Don't lie your yourself that your transformer is 480/(220/127). It means that this transformer can provide 220V of line voltage and 127V phase voltage?

If you connect this single phase 220V motor to a voltage 127V? How does it work?

Well it's down to our ALI99 to confirm the output voltage of the transformer. He states phase to phase and phase to neutral voltages. One has to assume he's right.

This could be tricky... Could we connect 220V single phase motor to two-hot lines of 220V?

Tony, I meant him.

Hehe From the voltage I'd guess it's one of those weird American things.

Where is Wikipedia from, from US?

I skimmed through it and found that American household can utilise two live wires to connect to general rotating machines. These machines will work out with lesser current.

So, two wire could be considered as two-phase? So you will be supplied with 240/120V single phase in US? Nevertheless, some of them are labeled to operate as two kinds of voltage? So, with two live wires connected to loads, you will say it two-phase of single-phase power?

Is this why Tony said "weird American thing"?

A typical U.S. residential 240/120 center-tapped system is still just a single phase. Larger appliances such as airconditioners, water heaters, and stoves are 240v, 1Φ; lights and convenience outlets are 120v, 1Φ. In most places, that is; you can get residential 3Φ, which you might want if you have a sizable hobby or cottage-industry workshop.

__C__
|.. |.. |
A--N--B

can represent a 3Φ 240/208/120 system. AB=BC=CA=240; AN=BN=120; CN=208 ("high leg"). A 1Φ 240/120 system is just A--N--B. (The dots are just to separate the vertical lines; the text system here does not preserve spaces, alas. [Ed. C.])

Tornado; I have not seen any residential neighborhoods with more than a single high voltage feeder, & single phase step down transformers, hi-voltage to 120/240 volt single phase to homes/houses. if you were to have 220 volt wye/star, you are right 220/127 volts. perry

That is certainly correct in our cities, and many rural communities. All the large appliances, such as stoves, are locally 240/120 single phase, ie 120/120 centre tap grounded. If you connect to a 3 phase 208/120 you notice a distinct drop in power when the high elements come on.

Tornado; NEC code is A to N, C to N, 120 volts. B to N 208 volts perry

Thanks for the correction; my fault for switching B and C. (Haven't seen a center-tapped Δ in a while.)

"Thanks for the correction; my fault for switching B and C. (Haven't seen a center-tapped Δ in a while.)"

Actually you were not necessarily wrong. Starting in the 2008 NEC, you can now mark the High leg as C instead of B, as long as the marking is clear. This was apparently something they had to do to accommodate some types of metering systems. I just read an article or two on it but didn't totally delve into the why's too much.

JRaef; The power company uses the high leg, right hand rule in their meter sockets to keep every thing uniform, & we did the same hi leg right hand in the panel boards. perry

dear must be a college student?

definitely, you can connect the 220v terminals across the motor.

All that will happen that un balanced current may flow thru the common point of secondary winding of transformer. If the star point is earthed, must be of strong cross section to take up that un balanced current.

Phase to phase is 220

Phase to neutral is 120

if we can connect then how technically connect two phase to one phase? is there any recommendation?

if can not then why?

The above "American thing" has said it all. Just go for phase to phase.

ALI99-

CAUTION! CAUTION! CAUTION!

This is not a simple question to answer since you have not given enough information particular to your situation. More information is needed to clearly answer what could potentially be a fatal answer. Much of what has already been given is full of presumptions and wrong answers. This could kill you or someone else who might think they have a similar situation. Look at some answers and they say the complete opposite of other answers.

Do yourself and others a very big favor, confer with someone who is very knowledgeable on the subject and can look at what you want to do and ask further questions. If you don't, it could be the most fatal question that was not asked!

One of the problems with this forum is that you can not confirm the knowledge of the repliers/posters. Some write very well but don't know much about the subject; some may not write so well but have the correct and safe answer; some have the right answer and can convey it well; some are completely wrong; and then there are some like me who don't reply to subjects that we are not extremely knowledgeable about but when we do answer about something we are fluent in we try to make our answers as clear and simple as possible.

Right now I don't have time to contribute to your questions but only two of the replies are correct (and they sound much different from each other)

Good Luck, old salt

You had the time to write your condemnation of answers given in good faith.

Why not the time to enlighten us all.

Is this a drive-by accusation? You allege a potentially lethal flaw in several answers, some of which could be mine, yet do not identify the flaw and how to correct it?

There could be an issue of just what is or is not grounded on the OP's motor. This has been mentioned briefly and could bear a further look.

I would be curious to know why this was considered OT, especially given the turn the discussion has taken.

Tornado-

Yours was not one of the poorer answers. I was the one who rated your post #10 as a good answer. Your answers have been well written and clear.

I was unable to expand upon my post technically due to several nieces and other relatives waiting for me for Easter Dinner. Those things happen just like I don't have time now to go into the technical details because I just returned home from the party and have to get some sleep in order to teach a class tomorrow.

Having conducted numerous Haz Ops and unfortunately several fatal accident investigations during my career I feel I would be remiss if I did not warn individuals that some of the posts have the potential to cause very bad situations. For example, a motor must always be grounded. If a internal wire were to come loose the frame would probably become hot to ground, a potential fatal situation.

Sorry, no more tonight. Got to get some sleep.

Good Luck, old salt

Most likely he has what we call a "high leg" or "red leg" delta secondary, it's common when there is only a small percentage of 1 phase loads here in the US. It's a 3 phase 240V delta secondary, but one set of windings is center tapped for a Neutral to be able to supply 120V loads. So A-B is 240V, B-C is 240V, C-A is 240V, A-N = 120V, C-N = 120V, B-N is 208V but you cannot use it.

All of that is immaterial to the issue at hand. A 240V (220V) motor can be connected between any two legs.

JRaef; why would you say that you cannot use the 208 volts from the hi leg? I have some 208 single phase motors that that wouldn't know better & go ahead & run. also many delta wound transformers only wind a single 120 volt winding from A or C, that way they save money. perry

"JRaef; why would you say that you cannot use the 208 volts from the hi leg? I have some 208 single phase motors that that wouldn't know better & go ahead & run. also many delta wound transformers only wind a single 120 volt winding from A or C, that way they save money. perry"

OK, maybe I should have said "should not use it". The problem is, 208V here is expected to be 208 Line to Line on a 208V system. In that High Leg delta system, 208V is Line to Neutral from the high leg and although technically something like a motor may not care, in practice if someone sees a single colored conductor along with a white conductor in a box, they might ASS-U-Me it is 120V by convention and cause a fire by hooking it to something not rated for 208V.

Problem #2 is that in many cases, the 120/240V 3 phase 4 wire delta service is dropped from an open delta transformer arrangement, where there are two transformers; one of them center tapped for the 120V lighting loads. So the Neutral reference is only technically present in that one transformer and if you load the High leg too much on that open delta, you may not get 208V out of it. I have heard tell of people getting only 190V. It was not intended to be used, so there are no design specs as to how it reacts to a Phase-to-Neutral connection.

If the motor windings are not grounded, Yes, connect up the 220 lines to the motor.

I assume the transformer is delta wye. ( Or is it a Scott T?)

Now the caveat. You need sufficient KVA for your motor. You will only be able to use 1/3 of the transformer rating. You will need to ensure additional loads are balanced on the other legs to not overload the windings.

GW; Da its a delta, why? could be a open delta, made with 2 single phase transformers, right? from a 3 phase source. why do you need to load the unused phases? guest

You don't need to load the unused phase(s). BUT if you add loads they need to balance the transformer. The single phase load is sitting on "one side". You don't just add up the kva, but need to distribute it correctly.