Connecting 480/277 Wye to Step Down Transformer

[GreenGuy]

Hey guys, I'm looking for some help from any commercial veterans that have ran into my scenario.

I will be installing some SMA Tripowers on a building with 120/208V. This installation will require a transformer. Unfortunately, I am stumped on how to connect a 480/277V Wye Inverter to a typical 480V Delta to 208 Wye Step Down Transformer. I do not believe that Wye to Wye transformers are readily available.

I talked to SMA but their tech support refused to give advice outside of their product (which is understandable I guess). I would use 208 inverters but I have limited wall space.

Have any of you guys wired a 4 wire 480/277 V Inverter into a 480V Delta transformer before? Any insight on how you did it would be appreciated.

 

[don_resqcapt19]

They make transformers with a 208 volt primary and a 480/277Y secondary. You don't need a wye to wye transformer. Even if the 208 to 480/277Y transformer has a delta primary it doesn't matter. All the primary is looking for is the correct voltage and it does not care if that voltage is supplied by a delta or a wye system.

 

[kwired]

Connect only the three phases to the input of the unit. Only use the source neutral for equipment grounding purposes and not as any kind of circuit conductor. That is how it is done all the time on any other 277/480 source, supplying such a transformer.

 

[ggunn]

They make transformers with a 208 volt primary and a 480/277Y secondary. You don't need a wye to wye transformer. Even if the 208 to 480/277Y transformer has a delta primary it doesn't matter. All the primary is looking for is the correct voltage and it does not care if that voltage is supplied by a delta or a wye system.

Sometimes it does matter. If the 480V inverter requires a neutral, then you will want it to be wye on the 480/277Y inverter side with the neutral tied to ground and delta on the 208V service side. We just installed one of these.