question

Have you contacted your local Victron Dealer for personal assistance with your Schematic Diagram?

Make sure you don't get a massive unbalance using that autotransformer with large inverters. It's exactly why some of us @Natebert and myself instead chose to have custom transformers built, you can see my comment and photo at this link at @Natebert has a post above it with more information:

https://community.victronenergy.com/questions/36781/using-autotransformer-to-create-120v240v-split-pha.html?childToView=212674#comment-212674

Direct link to Natebert's post:

https://community.victronenergy.com/questions/36781/using-autotransformer-to-create-120v240v-split-pha.html?childToView=81622#comment-81622

The 'real' question is, where are you getting a 15kva multi, (last time I checked, the largest multi was 5) or do you mean multi II?

PS: Nicely drafted schematic (cosmetically, I have no opinion re it's correctness or suitability for your situation).

Jennifer

I don't think you need an Autotransformer in this case.

You can accomplish split-phase with your two inverters without an Autotransformer. You connect the two inverters to each other with a cat5 cable so they can stay out-of-phase from each other, and you configure them with the Victron software as a split-phase pair. One will generate (or pass through) phase 1, and the other will generate (or pass through) phase 2.

You can use an Autotransformer with two inverters if you expect a load on one that is above it's capacity, while at the same time the other is below it's capacity.

As an example, I have two 3k Multiplus-II inverters (2.4kW continuous each) in this configuration with an Autotransformer (in the US with 120v split-phase). I have three devices that I want to run at the same time that each draw 1.3kW.

• Phase 1: 2 devices x 1.3kW => 2.6kW (.2kW above the 2.4kW capacity)
• Phase 2: 1 device x 1.3kW => 1.3kW (1.1kW available within the 2.4kW capacity)

Before adding the Autotransformer, if I ran both devices on Phase 1, that inverter would shut itself down as overload protection.

So what does the Autotransformer do? It takes from the spare capacity from Phase 2 and adds it onto Phase 1, allowing both inverters to run at roughly half the total load. So with the Autotransformer, I can run all three devices at once.

But if I had two 5k inverters (4kW continuous), I wouldn't need the Autotransformer at all, as the Phase 1 inverter could cover the full load on Phase 1 (2.6kW). This is more like the scenario you describe, with more than enough inverter for each phase.

Also, rather than using two sets of 4x 12V 100A in series, consider using 8x 48V in parallel. This would also let you start with any number and expand to any number. Each could be directly connected to your Victron Distributor or a Victron Power-In connected to your distributor with just 2AWG -- easier to work with vs 4/0 and less expensive.