How about Using a 1-Phase 120V to 3-Phase 240V Converter Instead of Parallel Inverters?

[MichaelK]

The cabin came with a small 12V solar system and I've been learning some things in the process of using and tending to it. I've had to replace the charge controller twice, the inverter twice, the battery chargers, and re-wire the circuit breaker box, and re-route the panel wires, and replace fuses and cutoffs, and so forth, and install a whole new battery bank. In fact, the only part of the system that I haven't replaced are the panels.

You know, I think people here, including myself, would find it very valuable to hear more about what the failures were? Can you go into more detail as to what went wrong with controllers and inverters? I'm guessing that your battery bank failed from inadequate charging? Big battery banks with small solar arrays were a thing back in the 90s. Why the rewiring?

 

[forbin]

I'd be happy to share my failures, which are many, and successes, which are fewer, but satisfying. I'll make some comments later today.

 

[forbin]

You know, I think people here, including myself, would find it very valuable to hear more about what the failures were? Can you go into more detail as to what went wrong with controllers and inverters? I'm guessing that your battery bank failed from inadequate charging? Big battery banks with small solar arrays were a thing back in the 90s. Why the rewiring?

The cabin was built, and the system installed, around the year 2000. When I bought it in 2019, the breaker box was rusty and falling off the wall. Inside it was a tangled mess. I installed a new box, new breakers, and ran the wires cleanly, but didn't do anything new or creative. I just wired everything the way it was already, but neatly. The battery bank is 8 x Trojan T105's in 4 parallel strings of 2. I'm now aware that it's a bad idea, but it's what I inherited from the previous owner. I replaced all the batteries with brand new ones, but I didn't really know how to care for them. I wasn't any good at measuring SOC or knowing how long to run the generator to fill them up. I under-charged, over-charged, partially charged, and subjected them to all manner of un-gentlemanly tortures. Recently, I got so busy at work that I didn't make time to maintain them, and the water levels got too low and exposed the tops of the plates. I filled them, but now the batteries can't handle any significant discharge. We can run our fans and computers, but any time the RV pump kicks in, the voltage drops too low and the transfer switch kicks over to shore power. Since there isn't any shore power, we either reset the switch or start the generator. (Oh yeah, I also replaced the transfer switch once. The original Iota ATS died due to bugs, birds, dirt, and humidity.) The batteries are my biggest failure. The rest of the system is just cheap. The original inverter, a Whistler 2000, just went bad, and the cheap Amazon one we bought to replace it went bad, too. The third one is a PowerMax PMX2000 and seems to work fine. The original charge controller was a $29 special that got blasted by lightning. We replaced it with another cheapo, which had wire holes that were too small for the solar cables, so (cover your ears) I actually snipped off a few of the conductors from the stranded wire to make them fit. That worried me, so I finally put in an Epever controller, re-terminated the cables, and it has worked well. Now I want to grow up and get some real equipment. That's my story.

 

[Supervstech]

Now for the pictures.

 

[forbin]

Now for the pictures.

Oh man, I couldn't. My skin is not that thick, and I'm sober.

 

[realpinochet]

Phase sequence. A split phase output from a paralleled set of inverters or an autotransformer gives you two waves of AC at 180deg off, so when one is peaking the other is at bottom.

On 3-phase your waves are 120deg off so when one leg is peaking the other two are only 2/3 of the way to where they're going.

Many people get the 240v versions of AIO's and put the 240v through an autotransformer to split the output into the two opposing wave forms, not uncommon at all.

There's been debate about this with signature solar selling the 240V growatt and using a auto transformer to provide the neutral; what if the auto transformer fails and you loose the neutral?

 

[Hedges]

Do you happen to know of an inexpensive ammeter that can record a valid peak amps value @Hedges ? I have a few clamp meters but none of them can capture the peak. There seems to be a lot that list that as a feature, but I don't want to just buy shots in the dark, myself.

I bought the Harbor Freight Ames 1000A one.

Key features for me were DC clamp amps, 0.01A resolution, 1000A on highest scale, inrush.

Want a meter that'll do everything, maybe not so cheap.

Want one meter, other than an oscilloscope, that can test all circuit component and measure everything. Even features I don't understand, yet. Cheap. Tired of learning I have the wrong tools.

diysolarforum.com

That may be accurate for motor starting surge of multiple cycles, haven't tried comparing to others.

It isn't fast enough for the less than one cycle inrush charging capacitors or starting up a transformer that saturates (For that I use a 20 kHz bandwidth fluke clamp probe and oscilloscope).
And I think "inrush" is only a feature it has on AC range, not DC.

 

[Hedges]

There's been debate about this with signature solar selling the 240V growatt and using a auto transformer to provide the neutral; what if the auto transformer fails and you loose the neutral?

Then bad things happen.
You could use theirs or another stand-alone autotransformer with suitable breaker configuration to avoid the issue.
Signature now sells one with breaker and relay that should fix the problem, OK I think for off-grid.
What I don't believe is that it also fixes the "trying to balance utility grid", "neutral bonding to ground" and "no objectionable current" issues. No schematics I've seen so far would allow connection to grid without some problem I could identify.

Victron appears to address all issues, because they also include a relay to switch neutral and bond it to ground.

Isolation transformer is another solution. Dumb passive big iron, not much can go wrong.

 

[copec]

I’ve been putting up this fellow’s install as an example of how it should be done with a grid connection:

There are used 480x240-240/120 transformers all over for relatively cheap.

If you aren’t doing a grid connection, I believe you would be fine with the autotransformer solution from Signature Solar, if going with that - even if passing through a generator at times.

 

[copec]

There's been debate about this with signature solar selling the 240V growatt and using a auto transformer to provide the neutral; what if the auto transformer fails and you loose the neutral?

I believe it has been worked out, except when passing through a grid connection. It’s pretty simple, you wire the inverter(s) and autotransformer together before a three pole breaker, so if it flips, it disconnects all power.