we are installing a 45kva array on our own building,the pv inverter is supplying 480/277 we are conneting to a 120/208 volt system. the inverter needs the grounded conducter in order for it to work correctly , do we bond xo and connect it to the inverter and the nuetral bar in our 120/208 volt panel?
Normally one would use a 480D/208Y xfm.
The UPS will likely have an output CB and the 480Y output neutral will be bonded at the cabinet. If there are no other loads besides the xfm, there is no need to extend the 480Y neutral.
The 208Y xfm secondary is treated as an SDS.
Typically you cannot use a 480V delta primary because the inverter needs the neutral as a voltage reference. ...
I'n not going to be any help. All my experience is with UPS inverters and apparently PV inverters are different than UPS inverters.
My expectation is if the inverter output needs a ground reference, then that would be provided by the NG bond at the first disconnect.
What I am hearing is, this PV inverter output will not support a delta resistive load. You have a 3ph inverter, but it won't run three phase loads unless the 3ph load has a neutral connection.
Interesting - but suprising
... I have been around this tree a few times; originally I was counseled by an inverter FAE to connect delta on the 208 side and wye on the 480 side, ...
Okay. You have experience and you have direction from the "inverter FAE"*
My recomendation is to follow your experience and the inverter FAE direction - What would we know any better than that.
originally I was counseled by an inverter FAE to connect delta on the 208 side and wye on the 480 side, but I found that transformers configured that way are not common. ...
I'm missing the point here.
208D/480Y transformers are plenty common, but likely not on the supplier shelf. You likely will have to order one. I suspect 480Y/208Y xfm are less common. I've never seen one. I've never seen an application for one. I highly suspect: Not on the shelf. You will have to order. And wait for one to get built. But I don't know that.
Regardless, I can't understand why you would consider a 480Y/240D xfm. Your connection is to a 208/120Y system. How are you going to do that with a 208D secondary?? Truly puzzling.
... One caveat, though; something I was told by the transformer companies is that 480/208 step up and step down transformers are not interchangeable.
This statement puzzles me completely. Could you be a bit more specific.
480D/208Y is different than a 208D/480Y - Yes that is true, but so what - you can't use a 208D secondary and you say the FAE says you can't use a 480D primary
208Y/480Y is different than a 480Y/208Y - I wouldn't have a clue here. But if an mfg rep told me that - i'd be asking for supporting test data
As I said, "Interesting"
I'm no help, but I am interested in how it works out. Always a good day to learn
ice
