TL;DR: I want to build a system that can take in split-phase 120/240VAC, single-phase 120VAC, or 12VDC, and always output split-phase 120/240VAC. I have a potential solution in mind using MultiPlus-II 2x120 + Autotransformer. Will it work? Are there better options?
I have a boat with a split-phase 120/240VAC system. Normally the two phases come from either 120/240VAC shore power, or from a split-phase generator. I'm considering an inverter setup that would allow me to create both legs from the inverter, and am imagining the following system:
Connect a MultiPlus-II 2x120 to the split-phase system. When the generator is on (or split-phase shore power is connected), it will pass through both legs. When single leg shore power is connected, or no input is provided, it will yield only single phase 120VAC.
I want to then connect the output of the MultiPlus to an autotransformer, such that:
- When the generator or split-phase shore power is being passed through, the autotransformer balanced loads between the two legs.
- When only single phase 120VAC is available, the autotransformer will convert it split-phase, creating the second leg.
Is such a configuration viable? Is it possible to wire the autotransformer in a way that achieves both of these purposes?
An alternative is just to use an 240VAC inverter with an autotransformers, but that seems to have the problem that it won't work when only single-phase 120VAC is available from shore power. Is there a workaround for that other than installing another transformer?
EDIT: Added diagram for clarity.