Question about Step-Up Step-Down Transformer Neutral Wiring

[Installer]

I'm wiring a 120/600 VAC Step up transformer and a 600/120 VAC Step down Transformer.
(PS I cant make the image any bigger, you have to right click on it and open in new tab)

I just wanted to make sure I have my wiring right at first but then I realized that I don't know what I am doing with the Neutral.
If A= 120 VAC ,is B 120 VAC or Neutral?
If C= 600 VAC, is D= 600 VAC or Neutral?
E= 120 VAC, is F = 120 VAC or Neutral?
Can anyone tell me what the correct way to connect the neutral is on the left side of the step up transformers?
Can anyone tell me what the correct way to derive the neutral is on the right side of the step down transformers?

Thank you in Advance

 

[LarryFine]

I just wanted to make sure I have my wiring right at first but then I realized that I don't know what I am doing with the Neutral.

You don't know what you're doing worse than you think, no insult intended.

You show the two 120v sections with the windings in series, but phased wrong. Presuming they're 120/240v low-voltage windings, they should be in parallel for 120v or in series for 240v.

Line A should connect to X1 and X3, and line B should connect to X2 and X4. The same with the output of the second transformer: line E from X1 and X3, and line F from X2 and X4.

(For 240v, X2 and X3 are tied together (only) with the lines to X1 and to X4. If you have 240v available, you can feed the first transformer with it to halve the primary current.)

If A= 120 VAC ,is B 120 VAC or Neutral?

That depends on which supply wire is the neutral. There will be 120v between A and B. If A is 120v to ground, B would be 0v to ground.

If C= 600 VAC, is D= 600 VAC or Neutral?

Neither is either unless/until you ground one of them. There will be 600v between C and D. If you ground one of them, the other will be 600v to ground.

E= 120 VAC, is F = 120 VAC or Neutral?

Same as above: Neither is either unless/until you ground one of them. There will be 120v between E and F. If you ground one of them, the other will be 120v to ground.

Can anyone tell me what the correct way to connect the neutral is on the left side of the step up transformers?

See above. There is no correct answer; it depends on how you wire the supply circuit to the primary terminals.

Can anyone tell me what the correct way to derive the neutral is on the right side of the step down transformers?

Again, see above. It depends on how you wire the secondary terminals to the world. Whichever you bond is the grounded conductor.

 

[electrofelon]

I concur with Larry. Here is a wiring diagram which may help. I am not sure if it is the same transformer, but the diagram should be the same:

https://temcoindustrial.com/mwdownloads/download/link/id/3448/

 

[Installer]

Thank you very much

Thank you very much

1. First of all Mr Fine, thank you very much for replying and taking the time. In self defense, when i don't know what I'm doing I stop and ask questions and don't move on until I have a solid answer. And I read all afternoon and could not find any information.

2. Whats going on is I have pair of existing 3 KVA 120/600 to 600/120 transformers, 1000' apart, supplying a remote weather sensor. The picture below shows the second transformer at the remote sensor.

3. At the transformer Output Side (the Right side of the diagram); X1 and X3 are tied together and I metered 120 VAC on X1 and X3 individually when I separated them.( Not 120 VAC between X1 and X3 --I put the probes on either X1 and Ground or X3 and Ground)

4. X2 and X4 are tied together, I didn't touch them.

5. I very respectfully disagree with your saying there will be 600V between C and D . I think their will be 600V at both C and D since they are on the same winding

5. I need to get some more power--20 A- another 600 feet away for a new station so I am replacing the these 3 KVA transformers with a pair of 5 KVA transformers

6. Then I would like to take the pair of 3 KVA transformers and reuse them for the new 600' feed.

7. That's when I started thinking--how do I derive a neutral at the second weather station? I'll have 2 120VAC lines plus no Neutral


7. Again thank you very much -Can you please wait until the morning after I do some sleep catch up and 4x cups coffee to further discuss.

8 (Please right click and Open new tab to see this picture full size)

You don't know what you're doing worse than you think, no insult intended.

You show the two 120v sections with the windings in series, but phased wrong. Presuming they're 120/240v low-voltage windings, they should be in parallel for 120v or in series for 240v.

Line A should connect to X1 and X3, and line B should connect to X2 and X4. The same with the output of the second transformer: line E from X1 and X3, and line F from X2 and X4.

(For 240v, X2 and X3 are tied together (only) with the lines to X1 and to X4. If you have 240v available, you can feed the first transformer with it to halve the primary current.)


That depends on which supply wire is the neutral. There will be 120v between A and B. If A is 120v to ground, B would be 0v to ground.


Neither is either unless/until you ground one of them. There will be 600v between C and D. If you ground one of them, the other will be 600v to ground.


Same as above: Neither is either unless/until you ground one of them. There will be 120v between E and F. If you ground one of them, the other will be 120v to ground.


See above. There is no correct answer; it depends on how you wire the supply circuit to the primary terminals.


Again, see above. It depends on how you wire the secondary terminals to the world. Whichever you bond is the grounded conductor.

 

[ActionDave]

...5. I very respectfully disagree with your saying there will be 600V between C and D . I think their will be 600V at both C and D since they are on the same winding

Larry is as knowledgeable as anybody on this forum, you disagreeing with him is on par with a little league baseball player telling Ted Williams how to swing a bat.

He is also really good at explaining stuff. Read this and it should give you a little better understanding of transformers and electrical systems....https://forums.mikeholt.com/showthread.php?t=189279

 

[Installer]

Hello , I apologize if I offended anyone, don't sleep much when I'm on the hotel
and it shows in my writing
i should be more humble because this forum has helped me tremendously.
Here's the diagram of the 3 KVA transformer. Thank you Mr Fine

 

[oldsparky52]

Larry is as knowledgeable as anybody on this forum, you disagreeing with him is on par with a little league baseball player telling Ted Williams how to swing a bat.

:lol: :thumbsup:

I agree, and you are funny.

 

[jim dungar]

...I metered 120 VAC on X1 and X3 individually when I separated them.( Not 120 VAC between X1 and X3 --I put the probes on either X1 and Ground or X3 and Ground)

When troubleshooting it is always a good idea to record all of the available voltage measurements. In you case this would be L1-G, L2-G, and L1-L2.

Transformer windings need to be connected to ground, in order to have a valid L-G voltage measurement. As Larry said, Neutral (well actually the grounded conductor) depends on which terminal you intentionally connect to ground. If there is no intentional connection to ground, you will get L-G voltage readings that can be confusing or unexpected.

I would suggest you review the existing connections. What you describe does not match the wiring diagram of the transformer you posted.

 

[Installer]

When troubleshooting it is always a good idea to record all of the available voltage measurements. In you case this would be L1-G, L2-G, and L1-L2.

Transformer windings need to be connected to ground, in order to have a valid L-G voltage measurement. As Larry said, Neutral (well actually the grounded conductor) depends on which terminal you intentionally connect to ground. If there is no intentional connection to ground, you will get L-G voltage readings that can be confusing or unexpected.

I would suggest you review the existing connections. What you describe does not match the wiring diagram of the transformer you posted.

I checked the connections.
The Transformer is very old and the Label is faded and the Diagram I posted is wrong.
-Its not the T-2-53113-1S. I guess that's the mistake.

But if you see the picture of the Wiring I took, we do have X1 and X3 each at 120VAC and X2 and X4 tied together for this transformer (whatever model it is)
And I would like to reuse them.

 

[Installer]

When troubleshooting it is always a good idea to record all of the available voltage measurements. In you case this would be L1-G, L2-G, and L1-L2.

Transformer windings need to be connected to ground, in order to have a valid L-G voltage measurement. As Larry said, Neutral (well actually the grounded conductor) depends on which terminal you intentionally connect to ground. If there is no intentional connection to ground, you will get L-G voltage readings that can be confusing or unexpected.

I would suggest you review the existing connections. What you describe does not match the wiring diagram of the transformer you posted.

I checked the connections.
The Transformer is very old and the Label is faded and the Diagram I posted is wrong.
-Its not the T-2-53113-1S. I guess that's the mistake.

But if you see the picture of the Wiring I took, we do have X1 and X3 each at 120VAC and X2 and X4 tied together for this transformer (whatever model it is)
And I would like to reuse them like this.

 

[kwired]

I checked the connections.
The Transformer is very old and the Label is faded and the Diagram I posted is wrong.
-Its not the T-2-53113-1S. I guess that's the mistake.

But if you see the picture of the Wiring I took, we do have X1 and X3 each at 120VAC and X2 and X4 tied together for this transformer (whatever model it is)
And I would like to reuse them like this.
View attachment 22787

120 volts to what?

As already mentioned if wired like drawn your low volt windings are in series with one another but are opposite polarity. Not sure exactly what that will do if you input 120 volts between A and B, magnetic effects will want to cancel one another, but wiring them in series you should be putting in 240 volts to get designed performance, but they need to be in phase and not opposing one another.

When you say 120 volts at each, but not to each other - you must be measuring to a ground reference? Voltage is between two points. If an item has a volt rating of 120 volts that ordinarily means between two input leads and not one lead to a ground reference, though one of the input leads may be a grounded conductor.

There is no neutral in a two wire circuit, one of the leads can be grounded. Systems with a neutral usually will ground the neutral conductor - NEC requires the neutral (when used) to be the grounded conductor most cases.

 

[Installer]

120 volts to what?

Ground.
The mistake here is actually not mine. I went out their and traced everything carefully, it is an Acme T-2-53113-1S
The pictures are below. Someone else did the wiring and I get 120 VAC at H1 to ground and H3 to ground

 

[jim dungar]

Ground.
The mistake here is actually not mine. I went out their and traced everything carefully, it is an Acme T-2-53113-1S
The pictures are below. Someone else did the wiring and I get 120 VAC at H1 to ground and H3 to ground

These pictures look similar to the wiring discussed by Larry. X1-X3-L1 and X2-X4-N(grounded conductor).

 

[oldsparky52]

In the OP's scenario, what should or should not be done on the 600V side of the step up transformer? Do you want to reference one leg of that 600V to ground or let it float? If you let it float, then you have to have an alarm system for a ground fault? If you ground one leg, does that create any other issues with having one conductor 600V to ground?

 

[oldsparky52]

To the OP, do you see that the pictures you posted don't match the wiring diagram you posted?

 

[kwired]

In the OP's scenario, what should or should not be done on the 600V side of the step up transformer? Do you want to reference one leg of that 600V to ground or let it float?

If you let it float, then you have to have an alarm system for a ground fault?

Simple indicator light that will likely be ignored is acceptable. First fault makes it a grounded system, second fault results in high current and trips overcurrent protection.

If you ground one leg, does that create any other issues with having one conductor 600V to ground?

No, just higher voltage to ground than many are accustomed to.

General rule is you still need to run a separate equipment grounding conductor, even if ungrounded though I think there is conditions where you can run just two wires in this situation if there are no other conductive paths for current flow between the two transformer locations

 

[Frank DuVal]

5. I very respectfully disagree with your saying there will be 600V between C and D . I think their will be 600V at both C and D since they are on the same winding

This is crazy. Larry is right. If no 600 volts between C and D in the diagram you drew, then there will be no 600 volts ANYWHERE! Look at the diagram again, see a ground connection anywhere, except for the winding shield? The winding shield is not in the circuit, just a safety item, no connection to any winding. Then you should not use a ground reference for ANY volt readings.

And read about how transformers work, a winding has at least two leads, with voltage developed between them. Not between them and some unconnected ground reference.

Larry is also right, polarity of the windings is important! Get it wrong on the secondary and the output voltage will be 0 volts. Get it wrong on the primary and the output will be 0 volts and LOTS of heat! Hopefully just a popped breaker/blown fuse, not actual fire....

 

[kwired]

This is crazy. Larry is right. If no 600 volts between C and D in the diagram you drew, then there will be no 600 volts ANYWHERE! Look at the diagram again, see a ground connection anywhere, except for the winding shield? The winding shield is not in the circuit, just a safety item, no connection to any winding. Then you should not use a ground reference for ANY volt readings.

And read about how transformers work, a winding has at least two leads, with voltage developed between them. Not between them and some unconnected ground reference.

Larry is also right, polarity of the windings is important! Get it wrong on the secondary and the output voltage will be 0 volts. Get it wrong on the primary and the output will be 0 volts and LOTS of heat! Hopefully just a popped breaker/blown fuse, not actual fire....

Which is what one should have if wired as drawn in the drawing in post 1. the two primary coils on the far left are drawn wired in opposite polarity. They will draw high current fighting one another and yield little magnetic effect for excitation of the secondary.

The two secondary coils on far right are also opposite polarity. Should there be any magnetism to create any excitation the two opposite polarity voltages will cancel one another out, is effectively like a buck transformer with 100% bucking voltage.

 

[Installer]

To the OP, do you see that the pictures you posted don't match the wiring diagram you posted?

Yes that's what's confusing me. Also I should have traced where the Ground and Neutral were coming from , that was my fault and its important. I also didn't check the Step Up side.

BTW I appreciate everyone's feedback and replies . Thank you very much, I've learned a lot from this post

BTW But its a bit confusing and humbling with everyone shouting at me so when I get to the Site I'll trace everything very very carefully on both sides

I'll take the New transformers for the Second Feed out of the box and see the leads,and set them up on a bench and test them and meter everything and try figure it out

I may be inexperienced but my parents were immigrants and I learned from them --If you hustle and are conscientious and work hard you will get there ,

 

[jim dungar]

Thank you very much, I've learned a lot from this post...

Thank you for continuing to be active in this discussion.