kdagley avatar image
kdagley asked

Two Multiplus in Parallel with one AC input at 50hz and one AC input at 60hz?

Can two Multiplus (Compact 1600s) run in parallel with one getting AC input from a 50hz generator and the other getting AC input from 60hz shore power? All other settings are the same and they are connected together on the AC outputs.

Right now they are sharing a single AC input with a physical switch to choose between Generator and Shore power input. I imagine that the 50hz Generator will not be running while 60hz Shore power is active, but it might occur. How would the Multiplus handle this? Could I set a Virtual Switch for this and maybe also set up a generator autostart/stop? I know individual Quatros allow dual AC inputs but it seems that dual Multis might work too.

Obviously the two frequencies cannot be combined, but could the shore power input run one Multi as a charger and the generator run the second Multi as an inverter/ power assist/ passthrough? If not, would the parallel Multis at least ignore one of the inputs?

The only downside to separating the AC inputs is that I assume only a Multi with an active AC input could charge the battery - essentially doubling my generator run-time when trying to quickly charge the battery as I do now using both Multis as chargers at once.

Any thoughts would be greatly appreciated!

MultiPlus Quattro Inverter Chargerbattery chargingGeneratorfrequency
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kai avatar image kai ♦ commented ·

Do you need 50 & 60 Hz at output?

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2 Answers
ben avatar image
ben answered ·

You can't feed two different waveforms into two multis and have them both share the same AC output, no.

You can have them both run from one (shared) input waveform, like it sounds like you already do. Then they are in parallel and must be configured to work together.

You can have one of them just be a battery charger and not connect to any AC loads while the other one passes through a different grid/provides battery assist. In that case you have two separate Victron systems, which may not be what you want.

Some of your other questions are confusing without a circuit diagram/picture. Maybe you can either follow up with one, and/or break your many questions up into separate posts here.

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kdagley avatar image
kdagley answered ·

Thanks for the quick replies!

I think what I need is an automatic transfer switch on the combined inputs so that when the generator autostarts, the shore is disconnected. I’m trying to make a system that is as hands-off as possible. I was just trying to avoid buying another device by using the built in switching in the Multiplus. All my equipment can run on either 50 or 60hz.

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ben avatar image ben ♦ commented ·

One thing I'm not sure about is how the inverter behaves if it is configured for 50Hz but receives 60Hz on its input. There's nothing in theory to prevent it from operating normally, but it might also reject that waveform (to protect your downstream equipment).

So you may find that, even if you install an ATS, you end up needing to reprogram your inverter each time you switch sources.

Separately, Quattro essentially provides an ATS inside. It has two inputs and will automatically prioritize one above the other.

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kdagley avatar image kdagley ben ♦ commented ·

My boat is European 230v/50hz and the parallel Multiplus are set to 50hz, but they work just fine when input is from the isolation transformer at 240v/60hz on a US dock. Power Assist even supplements at 60hz, but if shore power is suddenly cut, the inverters take over completely and it switches to 50hz. Happened yesterday and the AirCon (nameplated @ 50/60hz) seemed to take it with no complaints.

I wonder how two paralleled multis would normally handle two separate AC input sources. I ask because VEConfigure clearly shows this as a configuration option. Each supplied input might be at a slightly different voltage and frequency, like one at 225v/59hz and the other at 245v/61hz. Plus their phases may not be in sync either. How could these be combined to a single AC output? I'm guessing that it would either just pick one input and ignore the other or maybe even refuse to connect either input. It seems the best way would be to convert the inputs to DC (via charger) and then invert them back to a single AC output (at 50hz if desired), but I understand that a single Multiplus can only run in one mode at a time - not charge and invert at once. It would be great if one multi would automatically switch to charger-only on it's input while the other multi would supply it's input to the Output with power assist too. However, even this scenario would limit your output to just the capacity of one Multi, rather than the double power I now enjoy with them in parallel.

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ben avatar image ben ♦ kdagley commented ·

Thanks for confirming that the inverter will handle a different grid frequency gracefully.

It's very likely that the config option you're seeing for distinct inputs also presumes distinct outputs, like in a multi-phase system. But you want to combine the outputs, and that's not possible with different waveforms.

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