question

mike-lynch avatar image
mike-lynch asked

3 phase unbalanced load - no distributed neutral

Apologies in advance if this question has been answered somewhere else.

Please see attached diagram.

I have a customer that wants to operate CNC engineering equipment from a stand-alone supply. My question is regarding the equipment loading on the Quattro's. The CNC Mill has only a 3ph 3 wire connection to an onboard 400V to 200V transformer which also only has a 3 wire output. Assumption is a delta-delta connection as drawn.

I'm at saturation level with 3ph AC theory and understand what happens at the load end of the unbalanced 3 wire load but I can't find anything that explains how a single inverter in a 3ph config handle returning unbalanced current from the other two lines.

My questions:

Will this work?

If not, what would be needed to make it work?

Is this kind of connection supported by Victron at all?


Any thoughts and recommendations greatly appreciated.


ML.

MultiPlus Quattro Inverter Charger3 phase
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1 Answer
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Mike Lynch

such loads on the output are no problem, but the inverters do need a neutral connection for the input as you probably know.

also of course the neutral outputs of the inverters have to be connected to each other. just like any 3 phase Victron installation.


https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems

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mike-lynch avatar image mike-lynch commented ·

Hi @Daniël Boekel (Victron Energy Staff)

Thanks for your assistance. You didn't mention my schematic, but your comments appear to confirm that an output load of this nature as drawn is totally acceptable?

I had read the manual in your link, and was concerned about the following sentence:

"For units in 3 phase configuration: Our products have been designed for a star (Y) type three phase configuration. In a star configuration all neutrals are connected, a so called: “distributed neutral”. We do not support a delta (Δ) configuration. A delta configuration does not have a distributed neutral and will lead to certain inverter features not operating as expected."

I'm assuming then that this only refers to an installation where only the three active wires would be connected to the inverters - without the neutral at all?

Thanks again.

Best regards..........ML.

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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ mike-lynch commented ·

Hi @Mike Lynch

Ah I missed the diagram, yeah that's fine, don't forget to use correct protection for local regulations (I'd use 4 pole breaker, etc.)

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