# Transformer Wiring?



## Uglydog (Dec 11, 2015)

I'm puzzled again...
I'm reworking a Millrite with Z and X powerfeed. I've replaced the bevel gears in the knee, freed up the rust parts that are supposed to move and replaced the Z drive motor. The head and original Z drive motor were all 3 phase. Near as I can tell these 3phase was all that was fed into the machine. The main junction box fed directly into the old transformer box. Thus, 3phase to the transformer. 

The DC X axis motor is getting a complete rewire by a DC motor guru.
The transformer and box appears to have suffered significant internal heat. 
Thus, a new box and transformer. 

However, how do I hook this up to 220v 3 phase? Where does the third incoming leg go? Looks like I jump H1 and H3 and connect to incoming Line1. And jump H2 and H4 and connect to Line 2. Where does the third Line 3phase leg go? I didn't have much to start with when I got this trauma victim.

I need 1110v 1phase out to the DC motor.

The first pick is a close up of the old transformer, the second pic is the new.





Thanks all for your ongoing patience!
Daryl
MN


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## RJSakowski (Dec 11, 2015)

I'm not a 3 phase expert, but I don't think you can feed 3 phase into a single transformer.  You would need to have one transformer for each leg.  They may be housed in the same unit but there will be three cores, each with their own windings.  The two you have shown would be single phase running on one leg of the 3 phase.


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## Steve Shannon (Dec 11, 2015)

That's a single phase transformer. You hook one phase to it and take 120 vAC off the output for your controls, not your three phase motors. For them you just have the utility provide three phase at the needed voltage. 


Steve Shannon, P.E.


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## jim18655 (Dec 11, 2015)

That's a single phase transformer so it only needs 2 of the 3 phase leads. Connect  one of the 220 lines to  H1 and H3 the other to H2 and H4. You get 120 from the X1 and X2.


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## JimDawson (Dec 11, 2015)

jim18655 said:


> That's a single phase transformer so it only needs 2 of the 3 phase leads. Connect one of the 220 lines to H1 and H3 the other to H2 and H4. You get 120 from the X1 and X2.


:+1:


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## David VanNorman (Dec 11, 2015)

Do you have a Rotary  3 phase converter ? If you are running on just a spinner you might do well to take your 220 single phase of before the spinner. The spinner doesn't give true 3 phase . If you have true 3 phase it is no problem you can get your power from two legs of your 3 phase.


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## Uglydog (Dec 11, 2015)

Great!!  
Thank you All.
Cap off one leg.
Connect two of the 3 legs.

Is is silly for me to ask how a transformer makes a neutral out of two hots?

Daryl
MN


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## Uglydog (Dec 11, 2015)

David VanNorman,
I'm not familiar with the term "spinner" please explain.
The guy I'm doing this for runs a 50hp RPC. 
He is a weld fab guy, who runs large shears and benders.

Daryl
MN


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## JimDawson (Dec 11, 2015)

Uglydog said:


> Is is silly for me to ask how a transformer makes a neutral out of two hots?



You could ground X2 on the transformer, that would make it a neutral, which is described as ''a grounded current carrying conductor''  as opposed to a safety ground which is described as ''a grounded non-current carrying conductor''


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## jim18655 (Dec 11, 2015)

The transformer doesn't "create" the neutral it only transforms the voltage to 120v. You make the neutral when you bond one of the 120v legs to the frame of the machine. It doesn't matter which you bond to create the "grounded conductor" as long as you only connect one end the the winding. Get the elusive ohm meter out and check each 120v wire for continuity to the frame of the machine unless you can see the bond wire.


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## Uglydog (Dec 11, 2015)

Jim Dawson, "You could ground X2 on the transformer, that would make it a neutral, which is described as ''a grounded current carrying conductor'' as opposed to a safety ground which is described as ''a grounded non-current carrying conductor''"


Is it ideal to use ground as a neutral? Does this optimize electrical safety?
Searching for understanding...

Daryl
MN


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## JimDawson (Dec 11, 2015)

Uglydog said:


> Jim Dawson, "You could ground X2 on the transformer, that would make it a neutral, which is described as ''a grounded current carrying conductor'' as opposed to a safety ground which is described as ''a grounded non-current carrying conductor''"
> 
> 
> Is it ideal to use ground as a neutral? Does this optimize electrical safety?
> ...



While the neutral and ground are both grounded and are electrically the same, you would never use the ground as the other side of a circuit.  The ground is a safety ground to protect you in case of a short in the machine.  The ground (normally green or green/yellow) and neutral (normally white or gray) are separate conductors.

I hope that makes sense


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## Uglydog (Dec 11, 2015)

All,
I'm confused. Again.
If X2 is connected to both ground (machine) and the neutral of the DC motor wouldn't that make ground part of the circuit?

Daryl
MN


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## JimDawson (Dec 11, 2015)

There is no neutral on the DC motor, unless you are talking about the motor controller.  But technically the ground is electrically the same as the neutral.

Normally you would connect a white or gray wire to X2 of the transformer and run that to your device as a neutral.  The green ground wire would also be connected to X2 and go directly to the machine ground.  The motor controller should also have a ground lug that should be connected to the machine ground.


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## David VanNorman (Dec 11, 2015)

Uglydog said:


> David VanNorman,
> I'm not familiar with the term "spinner" please explain.
> The guy I'm doing this for runs a 50hp RPC.
> He is a weld fab guy, who runs large shears and benders.
> ...


 A spinner is a 3 phase motor started by a capacitor set up . It will give a third leg to your 3 phase motor but it will not be  a true 3 phase. I use it in my shop and it works well . A friend  used one to run some large  equipment . He started his with a rope.


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## Keith Foor (Dec 16, 2015)

Folks, if you don't know about electricity, or terms of it, please don't say anything.  
I am truly waiting on the post for someones widow that so and so was working on the wiring on their whatever and got electrocuted.

That being said.
The transformer in the picture is not 3 phase.  It can be used with 3 phase power, but it's not fed with all 3 phases.  
The reason it's labeled with 220 and 480 is that 220 or 480 3 phase is the voltage developed between any two phases of the line.  
As a side note, if you measure actual 3 phase to ground / neutral you get 277 for 480 and 120 if it's 208/220.
To feed the transformer you are going to hook 2 phases to it.  One will connect to H1 with a jumper over to H3 and the other phase will connect to H2 with a jumper to H4.  X1 and X2 are the 110 volt AC output that will run to the control circuits for the DC motor.  

On a side note, if you were to feed the transformer with 480.  The two phases would connect to H1 and H4 and a jumper would be placed between H2 and H3 for correct wiring.

And remember electricians or electric guru's are cheaper than doctor bills, lost wages and funerals.  
If you don't know for certain what you are doing, or feel the least bit of concern hire a professional or find a buddy that does this stuff and ply him with pizza and beer (beer after the work is done.  It saves in the long run


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## Bill C. (Dec 16, 2015)

I searched Google and found this; http://federalpacific.com/training/transformer-basics/chapter-3.htm.

I hate to say this but find a Master Journeyman Electrician who has experience in three phase industrial machine wiring.  So there will not be any damage if missed wired.  They should have all the meters and tools to get the job dine quickly. 

Good luck, be safe


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## rdhem2 (Dec 20, 2015)

Try this:

Neutral    White/neutral gray      Electrical ground       Return path for electrical current to source, all                                                                                                                       connections via electrical conductor to electrical
                                                                                                  source.  Only connects to physical/mechanical 
                                                                                                  ground at origination of electrical supply  to the building.

Ground    Green/yellow green     Mechanical equipment ground    Only carries fault current, Mechanical ground,                                                                                                                         Safety ground, connected to physical frame                                                                                                                             of equipment, purely for safety of personnel.                                                                                                                           Only connects to electrical ground (neutral)                                                                                                                             at origination of electrical supply to building.

Is it clicking yet?  
Post on mirror in bathroom so it can be studied while shaving your noggin!


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## Bill C. (Dec 20, 2015)

Uglydog said:


> Great!!
> Thank you All.
> Cap off one leg.
> Connect two of the 3 legs.
> ...



Try this page, http://diy.stackexchange.com/questions/33602/why-do-240v-circuits-not-require-neutral.  I am not much of a transformer guy but basically they use the center lug/tap of the transformer. 

Some integrated circuit chips require a neutral or zero voltage.  I have used two 9 volt batteries connected in series and used the connection between the two for zero.  I had a First Class Tech explain it me years ago.  I know it sounds crazy but it works.


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## John Hasler (Dec 20, 2015)

rdhem2 said:


> Only connects to electrical ground (neutral) at origination of electrical supply to building.


Or at the secondary of a transformer.


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## mksj (Dec 20, 2015)

The transformer output in this application is most likely floating relative to ground/neutral, and this is then rectified for DC, so there is no need to connect one leg of the transformer's secondary output to neutral. You would use the replacement transformer and wire it the same as the original one it replaced. It outputs single phase 120VAC which is just stepping down the voltage. DC output may be referenced to chassis ground through a center tapped transformer on the secondary or the negative DC rail in certain designs, but this is not applicable in this transformer.


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