Grounding the connected leads from the secondary of a transformer (Grounding H2-H3)

[ASomsak]

I am dealing with a GE 9T51B0012 transformer and it seems to be wired for 480 in 240 out. However it has been wired in a way I have never seen and was wondering if this was a legitimate way of wiring this or if it should be corrected. I have two legs of 480 running to H1 and H4 respectively and H2-H3 are connected; which seems normal. However on the secondary side have X4 going out as a leg, X1 as a leg, and X2-X3 are connected, but there are connected on the ground stud. I have a wire coming off of that. It seems they are using the wire coming off of X2-X3 + ground as a neutral along with X1 in some places on the machine for 120 but in other places they are using both X1 and X4 as 240. Can someone explain this, and or tell me if its correct.

 

[jim dungar]

What you describe is probably the most common transformer connection to provide 120/240V 1 phase 3 wire.

Your title inferred a wire on H2-H3, but there shouldn't be one there and you didn't mention one.

 

[BillyMac59]

Check the wiring diagram on the tranny's cover. I can't determine 100% without a picture but it sound like the secondary is wired for 120/240v. The X2/X3 point serves as the common/neutral. This point is normally grounded at the transformer. If the secondary winding are wired in series, it allows 240v only. If windings wired in parallel, it allows 120v only.

 

[augie47]

What you describe is "normal" for that transformer 240/120 secondary.

 

[LarryFine]

Welcome to the forum.

I have two legs of 480 running to H1 and H4 respectively and H2-H3 are connected; which seems normal.

That's a 240/480v primary, wired in series for 480v. The H2-H3 junction is (and should be) floating.

However on the secondary side have X4 going out as a leg, X1 as a leg, and X2-X3 are connected, but there are connected on the ground stud. I have a wire coming off of that. It seems they are using the wire coming off of X2-X3 + ground as a neutral along with X1 in some places on the machine for 120 but in other places they are using both X1 and X4 as 240.

That's a 120/240v secondary, wired in series for 240v. And yes,the X2-X3 point is the grounded neutral.

That's how the secondary of most utility transformers are wired; two secondaries in series or parallel.

 

[ASomsak]

I just find it odd that I cannot find any other documentation on this subject or around these trans formers. But from what I am understanding it is wired and being used properly?

 

[infinity]

I just find it odd that I cannot find any other documentation on this subject or around these transformers. But from what I am understanding it is wired and being used properly?

Yes it is wired correctly. The GEC should connect to the X2-X3 junction.

 

[petersonra]

I just find it odd that I cannot find any other documentation on this subject or around these trans formers. But from what I am understanding it is wired and being used properly?

It is not unusual for a transformer diagram not to show specific wiring because they can often be wired in multiple ways depending on the application. I think what you have is probably just fine.