Three phase transformer connections

[byzman]

I am looking for information on connecting three single phase transformers to make a three phase bank. We requested a 480Y/277 volt service, but utility provided a 120/240 volt service with a center tapped nuetral. The loads are all three phase(there are no 277 volt loads). The primary is connected as WYE (all of the H2 terminals connected), but they are not grounded on the primary side. The primary neutral conductor is only connected to the secondary neutral conductor which runs right to our equipment. It does not appear that the transformer bank is grounded, except through our service grounding electrode. If the 480Y/277 system is better we would like to have it changed, but if there is no difference we do not want to hassle the utility. Any reference materials you could recommend would also be helpful. Thanks.

 

[dpc]

If you have equipment that requires 480V, 3-phase power, then I don't see how a single phase 120/240V service is going to work at all. Unless I'm missing something, I think the utility will need to give you a 480V secondary.

The service needs to match the electrical system it is serving.

 

[busbar]

dpc, it sounds like byzman may also be describing a 3ø4w system, but should be referred to 240/120 if that is indeed the case. It seems very difficult to imagine that a utility would goof up such a request. What form of request for servce was forwarded to the utility? Certainly it was not completely verbal. Where was the breakdown in communication? byzman, unless I am also completely misunderstanding something, you need a qualified industrial electrical contractor to design a code-compliant system for your machine tools, along with filing for permits and inspections. I do not expect that a contractor would accept the liability for an installation by others.

“…do not want to hassle the utility.” Huh?

It doesn't add up. Your needs seem way beyond what message-board postings and web links can address.