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Running a single phase of a 3 phase system off an inverter


L0rd0fCha0s

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Hi everyone

Just looking for some input here.

At my workshop, we have a 3 phase and neutral in feed to our main DB.

I have then run a 4 core +earth EEC cable from the main DB to a Sub DB where 3 single phase loads are connected.

Question:

Am I able to power one of the phases off my Growatt SPF 3000TL HVM-48?

The plan would be to feed Neutral and L1 into the Growatt from main DB, and then into 2 of the cores in the ECC.

Then the other two cores of the ECC will be connected directly to L2 and L3 in main DB.

When in feed is on, the Growatt will be doing nothing, so the ECC will receive 3 phase power from the in feed.

When load shedding happens, L2 and L3 will go down and the Growatt will still supply L1.

I will not be running any 3 phase load off the sub DB, only single phase loads.

Will this work?

I understand the current in the neutral wire of a balanced 3 phase system is zero, but the system will not always be balanced in my case.

So the Growatt Neutral may see more/less current than what is going through L1 when power is on, but current in Neutral and L1 will be equal when mains is off and Growatt is operating.

One concern is that when power is restored, the Growatt takes a second or two to switch its load back to the infeed, during this time L2 and L3 will be live but possibly unable to have a return path through Neutral due to the Growatt being in operation.

The backup (perhaps safer) plan would be to use the 4 cores in the ECC to run L1 N1 and L2 N2 so the Growatt has its own independent L1 and N1 outputs, with L2 being connected to one of the phases and N2 terminated to the common Neutral in the main DB - this will work but will reduce the maximum amount of power I could deliver over the ECC cable.

Any input is appreciated.

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