We're installing 167 KW of 480V inverters in a building that has a 120/208V wye service. The inverters need a neutral, so we'll be using a 480/277V wye - 208V delta transformer (225 KVA).
Looking at a similar (almost identical) installation, I saw they used a Hammond HPS Sentinel G transformer marked "Inrush: 15X (Max) / Suitable for PV/Solar Bi-directional use".
Our distributor has proposed the same transformer except
that it's marked "Transformer suitable for step up operation only" in place of the markings noted above. It's a stock item, whereas the PV-rated unit has a longer lead time and is more expensive.
A transformer in a PV system like this is an interesting case because the roles of primary and secondary reverse from startup to production operation. When the installation is initially energized, the 208V side will be the primary with little or no secondary load because the inverters will be dormant. But once the inverters begin producing, the 480V side will become the primary, feeding the inverter output to the building through the 208 secondary.
I've learned there are a several factors to consider, as described in these links: Reverse Feeding Dry-Type TransformersCan a transformer be back-fed or used in reverse?