3 phase machine

Have a 3 phase wiring question. Have received a new production machine at work. 220v 3 phase. I have a 220v 3 phase circuit available. As I understand it, two of these
legs are the same, and the 3rd is different. On my supply, I know which is which. The machine has three wire input: red, blue, black. Which are the 2 that are the
same? Or am I off base here? Thanks
 
There is a delta or wye configuration, need to know what shop is wired for, would suspect wye.

The three conductors are essentially equal, hook 1 to each phase, reverse any two wires if it turns backwards.

You will need an ground connector, there is no neutral on 3 phase.
 
Please hire a licensed electrician when hooking up 3 phase at work, if you are not completely sure.
 
My son just went through one of these nightmares in his new shop. The engine dyno needed three phase 480 and all they had was single phase 220. They got it wired up with converters,inverters,diverters,you name it. It put them way over budget,but they got her going. I guess anything's possible if you spend enough money.
 
I work in this industry, it is amazing how many companies buy a piece of equipment with no plan on how to connect it.

I have even seen people bring in unplanned substations and MCC,s
 
Like David G said it depends on delta or wye winding. Measure each phase to ground.If you know your supply has a high leg ,as you seem to, then you have a delta set up.
 
My shop has 240 3 phase. two phases 120v to ground/240 phase to phase, third measures 218v to ground. and there is a neutral used for my 120v needs with one of the two 120 phases.

Most are not like this for sure, but they do exist.
 
If machine uses any 110v control circuits, you can not 'simply connect the 3 phases & reverse if run wrong direction' when it is supplied with a high leg delta. You will run risk of burning some control circuits.
 
As far as the machine goes it will not make any difference except motor direction. Switch any two wires will change the motor direction. All of my machines are 440 and they have the step down transformers to run relays and computer controls. My surface grinders are 200 and I hung a step down transformer in the tool room for them. I have a step down transformers thru out the factory for my single phase 220/100 panels.

The power company has one leg of their transformers grounded at the pole which I don't like and makes it read different to ground but still the same from one leg to the other in any combination.

Not that big of a deal unless your trying to do it hot.
 
Thanks for the responses...yes, I wish there was someone else to do this too, but things don't always work that way. Sometimes you have to deal with what you got.
I think I mis-wrote...my mind was on a previous project. Each leg measures 124 volts to ground and 212 volts leg to leg. There is no data plate on machine. thanks
 
With three phase from a utility company all three wires are the same voltage. You get the 220v by putting a meter on any two wires. If you were using a rotary phase converter then the voltage on L3, the blue wire would be more. This compensates for only having actually two hot lines.
 
Would that be a 208/120 Y?

I really would not hook up a machine without the motor nameplate or manual.
 
Typically the "high leg" goes to the middle. No particular reason, that's just the way most do it.

It really doesn't matter as there is a control transformer that drops the voltage for the controls. It doesn't care so long as it gets any 2 legs.

Wire it up, turn it on and check the rotation. There is a 99% chance it will be wrong, just because...
 
It is code for it to be "B " phase or center in panel . In meter pan it goes on the right. Taped orange not red as redleg is just an expression .
 
That is wye not delta { should be a straight hook up any three wires to ant three terminals--- check rotation -- for things that cannot be rotated backwards .use a phase meter to predetermine rotation].
 
(quoted from post at 14:56:06 01/17/17) machine could be 220 delta, need plate off motor

Doesn't matter to the machine if the source is 3 phase 208/220/240 from either a wye or a normal delta transformer.
That said those corner grounded delta systems are best avoided . They were a compromise intended to save $$$
 
I got to think about this in my steroid controlled mind.

The amp rating on the circuit will have to be increased due to the lower voltage.

Are we sure this is 240 V machine without stickers?
 
Steve you have that right. Down at work one of the guys who should know better put a new 2hp pump on the Hobart dish machine. Why would it not pump right and would trip off on thermal overload? Yes, swap two wires .
 
David, it is probably set up for 240v, but he's running it on 208.

It will probably work, just depends on how close to max the motor(s) are loaded.
 
Hire an electrician, the money you spend, will be well spent. Funerals are very expensive. joe 40 years an electrician and retired!
 
As sometimes (NOT always) happens when an electrical question is posed you get MANY different opinions/answers, some right some wrong, some lay some professional, so I will try my best to clear things up IF THATS POSSIBLE LOL

When you speak of Three Phase 220 volt (modern is 240), some (NOT all) lay persons may NOT understand the differences between


A) A 240 volt Three Phase Three Wire (Ungrounded) DELTA which ONLY has 3 wires and its 240 SINGLE PHASE from any one leg to another WITH NO 120 VOLT AVAILABLE, but its 240 Volt Three Phase if you use all three legs........

B) A 120/240 Volt Three Phase Four Wire Grounded Red/High Leg Delta. On that system on the one transformer that has a center tapped grounded Neutral, you would get 120 VAC Single Phase from A or B to the grounded Neutral, but from the other Red/High Leg (which isn't used) it would be 208 to Neutral. If you wire across any of the three transformer ends you would get 240 Single Phase but out on the ends of all three transformers you would get 240 VAC Three Phase

C) 208 Y 120 Three Phase Four Wire Grounded Neutral. On that its 120 VAC Single Phase from any of the three legs to Neutral but 208 Three Phase if you use all three.

The system used depends on the loads in the building, in my career I had occasion to use all three

BOTTOM LINE if you don't know which of the above three 240 three phase services you have AND DONT UNDERSTAND THEM OR YOUR LOAD, CONSULT A TRAINED COMPETENT PROFESSIONAL ELECTRICIAN versus anything said here ME INCLUDED as I'm long retired from electrical power distribution design.

John T
 
With all due respect to your statement in an attempt to add to and clarify for some here, I will add:

"With three phase from a utility company all three wires are the same voltage"

If its 208 Y 120 Volt Three Phase Four Wire that's TRUE all three wires are 120 to Neutral and 208 line to line.

If its 120/240 Three Phase Four Wire Red/High Leg DELTA which has one transformer center tapped (Neutral), two wires are 120
to Neutral but the red/high leg is 208 to Neutral, its 240 of course across any transformer ends.

If its 240 volt Three Phase Three Wire straight pure DELTA (no 120 available) again its TRUE its 240 across any transformer

My post above may help also

John T
 
John,

Thanks for describing the delta configurations, I think it has been 25 years since I have seen it.
 
Youre most welcome, actually all three of the possible 240/208 three phase systems are fairly common out there depending on the buildings electrical use.

John T
 
I got nailed once on a 480 isolated system that one leg had gone to ground. I got it from ground to one of the still hot legs.
That hurt.

Dusty
 

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