At home we have three 127v AC power supply, 120° from one another. I want to install grid tied PV array, and the project approved by the electrical company displays a single phase inverter connected to two out of the three phases available at home (I guess I'll have to choose the phase with higher load or something like that). The inverter in question is this one.
The problem is: nowhere in the manufacturer's manual such weird configuration seems advised. It is explicitly stated that it is a single phase device, and I must connect L, N and PE on the AC side of the inverter, which I take L to be the phase, N the neutral, an PE the ground (which is shorted to the neutral inside the electric box at home). I assume the project advises to connect ground to PE, phase 1 to L, phase 2 to N, and leave phase 3 out.
How is this supposed to work? Only one phase will be powered by the inverter and the other will be used simply as reference? Can it damage the equipment? Is such installation common?
Best Answer
Looks fine to me. Consult with the manufacturer to assure the machine is internally built to be able to accept line wire on the "N" terminal. I expect it will be -- they couldn't sell any in North America/Colombia if not.
You have 3-phase "wye" power, Brazilian style. A single-phase load could either go corner-neutral (127V) or go corner-corner (220V).
When you're backfeeding into the grid at a small scale, the same applies to feeds as loads. Since you can attach a single-phase 220V load to A-B, you can also attach a single-phase backfeed there.
It does not matter to which phases your house's loads are attached, because you know of course that a grid-tied solar inverter is totally incapable of creating power for your local use during power outages. That is not what grid-tied inverters do. If you want that ability, things get more complicated.