question

Problems with running two quattros in parrallel with autotransformer

I'm perplexed. Perhaps someone here can help.

I have a completely off-grid system. I've been running a single quattro to an autotransformer to step up the output to split phase 110/220. It works great. I'm adding a second quattro to support additional load. I've rewired the autotransformer and the quattro AC outputs to look exactly like :

I then created a new bus configuration setting it to two phase 180 degree.

When I turn on the breaker on the autotransformer, there is about 1500W that loop between the two legs.

This isn't normal, is it?

victwiring.png (327.6 KiB)
victwiring2.png (44.2 KiB)

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Me parece que no tienes que configurarlo como dos fases 180 grados. Tienes que configurarlo como dos inversores en paralelo.

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I'm attempting to utilize the autotransformers balancing. The manual shows this:

capture.png (71.6 KiB)

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I sure would love some input. I've rewired to bypass the autotransformer and everything is working as it should. I'd like to be able to utilize the balancing feature of the autotransformer. The above image seems clear. The neutrals from the two AC sources are tied together and the two 120v hot lines are on the ends of the coils. The issue I'm having recurs if I wire it that way.

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You says you "have a completely off-grid system" but then show a grid input. Do you get circulating current when the grid is connected or when off-grid? It is possible your incoming grid is not quite balanced. Or the turns ratio of the transformer is a bit out. In which case you might need to trim the output voltages of the two inverters. You will need to check the various voltages under a variety of conditions with a decent voltmeter to track it down.

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I have no grid. I was looking at that second diagram as the two AC outs from the two quattros. In the autotransformer, I'm splicing the to neutrals coming from the quattros and wiring the hot lines into the input breaker. The grounds from the incoming ac are also tied and wired to the autotransformers ground.
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