Transformer question

[souvik]

HI, this is my first post so in case i have done it under the wrong group. Please feel free to direct me to the right place.

My question is:

I have an inverter having a 3phase, 4 wire wye output at 480V. Can I feed this to the delta of a step down transformer if we bond the neutral from the inverter to the ground before entering the building? The other side of the transformer is a 208/120V wye connection.

Thanks is advance

 

[GoldDigger]

No.
The neutral terminal of the inverter must be connected to the center point of a wye transformer winding.
Other than adding a zig-zag grounding transformer to the configuration there is no way that you can connect the inverter to a transformer delta. And the AHJ may not accept a grounding transformer either.

On the grid side of the transformer, you should not connect the center point of the wye winding to anything.
Basically what you propose is just not the correct transformer. Technically, you need a step UP transformer, with the nominal primary on the grid side. That step UP would have a delta or wye primary and a wye secondary.

 

[ron]

I'm guessing the inverter is a separately derived source, like a UPS output?

If so, then you would bond the N-G at the inverter output, then run to the delta primary without a grounded / neutral conductor.

 

[GoldDigger]

My response was based, perhaps incorrectly, on the assumption that the OP was talking about a grid-interactive inverter (i.e. PV).
If the reference is to a standalone power source, UPS or otherwise, then much of my details are wrong and the transformer may actually be suitable if the wye output of a grounded SDS is connected to a delta primary.