Grid Tied Inverter On 4 Wire Delta System

[Sunfarmer]

An interesting problem has occured on some recently installed PV installations. On the most project there are 4-240 volt single phase grid-tied inverters connected to a 240V/3P/4W Delta electrical system. L1 & L2 of inverter 1 or I1 are connected across phases A-B respectively, I2 across C(L1)-A(L2), I3 across B(L1)-C(L2)and I4 across C(L2)-A(L1). The neutral is tapped on the utility transformer at the center of A-C. When connected like this, inverter 1 and only inverter 1 will not connect to the grid(this means any inverter in position 1 has the same failure), the failure shows up as a XFMR Disturbance, meaning a utility transformer problem. But, if the line leads for are reversed, meaning phase A to L2, B to L1. The inverter starts right up every time. This same problem occurs only and on every 240V/3P/4W Delta project. I believe the problem is something inherent to the Delta system itself and not the cause of system loads, but I need some help explaining why this works.

 

[abcd3286]

RU sure you are not connecting from A to the center tap. Gottal watch out for wild leg connections.

 

[Sunfarmer]

There is no neutral at the inverter, connections are as previously explained.