How to use single phase 220VAC inverter in split phase setup

[azaxi]

I have VMII-PLUS-5.5KW hybrid inverter. It has 220V AC IN marked as L, N and ground, see picture

In Canada, we have two 110V lines L1, L2 with reversed phase and N and ground are middle.

I plan to connect L1 to AC IN L, L2 to AC IN N and ground to inverter's ground.

Inverter makes no assumption about N being ground, I checked resistance between N and ground, there was some momentary resistance, but in few seconds went to infinity.

When running from utility power, center potential is provided by source. But when running from batteries, there is no center potential and if connected to distribution panel directly, L1 or L2 voltages would be undefined depending what appliances are connected. So I need to recreate center potential.

Is it possible to use 220/110 step down transformer to create the split potential and use it as neutral/ground like shown below ? I believe there would be high ground currents.

 

[rjenkinsgb]

The installation manual for that does not include anything about isolation between sections, so there is no way of knowing for sure what will happen if you operate it with L2 connected to Neutral.

It may work, or it may blow the unit; the normal assumption is that there is little voltage between neutral and ground - though I'd expect a well-designed device to be able to stand reversed L-N inputs.

It apparently has a direct bypass while AC input is present, so the input & output may then be linked by a relay or contactor.

If you try it, I'd also check for AC leakage on the battery and solar panel terminals... There should not be any, but anything is possible, depending on the designer and what AC connections they expected.


For the centre tap output, you could use an autotransformer or a dual-primary transformer (eg. one with 2 x 110V or 2 x 115V, for series or parallel connection) with the primaries in series and the virtual "neutral" from the centre tap.
(Leave the secondary disconnected; the voltage of that does not matter).

That would likely give better balance that using a secondary winding.

 

[MaxHeadRoom78]

Normally in N.A. when using equipment, inverters, VFD's etc, shown as 230v L1 & N, all you need to do is use the L1 L2 240vac there is no Neutral used or needed.??
(i.e. The equipemnt does not know the difference.)
You do use the GND however for the earth terminal.

 

[azaxi]

Normally in N.A. when using equipment, inverters, VFD's etc, shown as 230v L1 & N, all you need to do is use the L1 L2 240vac there is no Neutral used or needed.??
(i.e. The equipemnt does not know the difference.)
You do use the GND however for the earth terminal.

Usually equipment should not know the difference, but inverter is a power source. I am not so deeply involved in power electronics and do not know the code, but for example, Champion 42451 generator does not connect neutral to ground, but BG6250E does (see wiring on page 47). Both are sold on Canadian market by major retailers and must have passed safety inspections.

If this hybrid inverter internally connected neutral and ground, powering from BG6250E connecting generator's L2 to inverter's AC IN N would result in dead short.

Thanks rjenkinsgb.

My schematic in first post may be incorrect. I think those inexpensive Chinese step-down transformers on Amazon, that are rated for 30min of stated load, are actually auto-transformers.

My needs for 110V are small. Most demanding loads will be 110V/15A, one at a time or very occasionally two that would be running from opposite phase. Automatic loads, like well pump and water heater, are 220V.

For now have the 3kVA uncertified transformer, but I think for certifiable installation will need something like this.

The problem I see is that if L1 and L2 are not evenly loaded, virtual neutral and utility neutral may have different voltage resulting in ground currents.