Hello to everybody. Asking for opinion. System before, off grid single multi 48V 5000 with single ac coupling lithium batteries and 3 phase generator and between generator and AC in multi, there is a transformer 400V in and 240V out (for balance the 3 phase of the generator) The 3 phase generator necessary because of a 400V ground water pump. (so I need run the generator to get water) Now I got 2 multis more, and made a 3 phase off grid system, so I can run the water pump without generator. Everything looks good. My thinking was to put the transformer between multis and load… (reason is because old house with only 1 line, and pretty complicate to distribute the loads on the 3 phase, and this way balance the multis) I did, and it seems to work (only one strange thing, 1 of the phase of the transformer has much more load then the other 2…(example: load 5400w = L1 570w L2 1000w L3 3750w, don´t know why? is that normal?) Do somebody see inconvenience using the transformer? Can it harm the system?
And here by maybe an other question, can I connect a single AC coupling (with assistant) to a 3 phase offgrid? If yes where should I connect AC? To one multi, or 240V out transformer?
Looking forward hearing opinion and thanks in advance
You cant transform threephase input into singlephase output while the input is equally loaded (with a transformer. Rotary converters and VFDs aside). Theres always going to be a load difference on the threephase side. There are windingtypes that allow for some load spreading over all three input phases, but none achieves a truly symmetrical distribution with singlephase output.
The most basic form is an open-delta, which only loads two of the three input phases. A zig-zag transformer with purely singlephase load will show 2:1:1 distribution. Then theres more specialized types like a Scott-T or LeBlanc.
I would attach the AC coupled PV directly to the MP output, since then the power figures match. Choose the one that sees the most load from the transformer, so in your example L3.
I personally dont see the need for any of this. You had a working singlephase system, with singlephase loads and singlephase AC coupled PV. The only thing that needed threephase was the waterpump, which could have been exchanged by a singlephase model or driven by a VFD. But thats a bit late now.
Hi Chrigu, thanks for your opinion! I´m learning, and wanted to experience how to configure a 3 phase, and see the benefits. The need? you are right! But I wanted more power, so or parallel or 3 phase. And I was thinking change water pump, but 135 m under the ground, 200 m horizontal distance, so you need big pump much load to get water at the end, that´s also a big story and costs… Sorry the question, what is driven by a VFD? What is VFD?
Variable Frequency Drive. Many can take single phase input and create threephase output to run a motor. They dont get too big, since usually 230V singlephase is limited to 16A or 3.6kW. As long as your pump is under that, you could run your threephase motor off of single phase supply
Hi, with single multi, I´m able to configure a AC Coupling, but how configure only 1 ac coupling with a 3 phase? I opened ve.configure, selected the multi I wanted to ad ac coupling, add assistent, PV Inverter support, only thing what appears is VE.Bus BMS yes or no. and it says an ac coupling to each multi and the same loads…, and then no options for parameter…
You add the assistant to the L1 master, through VE.Bus Config, then copy that to the other two units. Only the L1 master holds the main information, the others only get the assistant
I did, and it looks it´s working. But wrong reading of the values on touch screen! It´s a 5kw PV inverter and 3Kw panels. In the configuration of the master L1 I put 5000w Inverter value and 3000w panels value, and then copy it to each other multi…The PV inverter in this case I connected it to L3
