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I Can't Afford So-Called "Tier 1" Equipment. What's Good at Tier 2?

Mattb4 said:
Saying something is junk because it is not UL listed is a incorrect view of things. There can be a range of quality in the Tier None products. Victron sells some non UL listed components. It however has a good reputation for reliability and engineering standards.
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That is true, but your homeowners insurance company may have a say about that, so I think insurability needs to be part of the criteria.
I have both SMA and MPP. The MPP units are UL listed and have WAY more capability, but their documentation, software/firmware is suspect.
The SMA's have been running non-stop with zero issues since 2008, and are still perfect. That right there puts them in Tier 0 status by me. Cost doee not mean better. My neighbor has constant issues with their Sol-Ark(Deye), which cost way more than SMA and MPP.
 
42OhmsPA said:
After the inverter before the 120/240vac loads panel.
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In that case, I think wiring a 240/480 primary, 120/240 secondary transformer with 240 || 240 driven by 240V from inverter(s) will draw relatively high no-load current. They are designed cheap, allowed to partially saturate.

The two 240V primary windings in series would make a nice auto-transformer for 120/240V. That will have low idle current, about 1/10th as much (and reduced power handling compared to nameplate.) But using it as isolation transformer, output in series 120/240V windings would only produce 120V.

I would need other windings or a differently wound transformer to get 120/240V split phase out.

Check out my current measurements and waveforms. Secondary 120V driven 120V, primary 240V driven 120V, primary 240V driven 240V.

diysolarforum.com

transformer excitation current - isolation transformer used as auto-transformer

So you think you can backfeed a transformer secondary, either as step-up or as auto-transformer? Turns out these things aren't so ideal and reversible as one might expect. It isn't just the greater inrush (primary is often wound outside secondary to reduce inrush current), but also idle current...
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timselectric said:
Copper or aluminum.
Weight and heat tolerance.
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And efficiency (I think) and price.
Aluminum requires thicker conductors, so current flow is further from core, less coupling. But maybe that's not a bug, it's a feature.
Some of my transformers have multiple windings with about 1/2" gap between layers. Air flow and more leakage inductance. Copper or aluminum would be similar if not packed tightly.
 
Hedges said:
In that case, I think wiring a 240/480 primary, 120/240 secondary transformer with 240 || 240 driven by 240V from inverter(s) will draw relatively high no-load current. They are designed cheap, allowed to partially saturate.

The two 240V primary windings in series would make a nice auto-transformer for 120/240V. That will have low idle current, about 1/10th as much (and reduced power handling compared to nameplate.) But using it as isolation transformer, output in series 120/240V windings would only produce 120V.

I would need other windings or a differently wound transformer to get 120/240V split phase out.

Check out my current measurements and waveforms. Secondary 120V driven 120V, primary 240V driven 120V, primary 240V driven 240V.

diysolarforum.com

transformer excitation current - isolation transformer used as auto-transformer

So you think you can backfeed a transformer secondary, either as step-up or as auto-transformer? Turns out these things aren't so ideal and reversible as one might expect. It isn't just the greater inrush (primary is often wound outside secondary to reduce inrush current), but also idle current...
diysolarforum.com diysolarforum.com
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You kinda lost me, I need to read it about 6 more times. ?

If I'm understanding, you're saying wiring 230 EU inverters to each primary would work nicely for US 120/240 output?
Hedges said:
And efficiency (I think) and price.
Aluminum requires thicker conductors, so current flow is further from core, less coupling. But maybe that's not a bug, it's a feature.
Some of my transformers have multiple windings with about 1/2" gap between layers. Air flow and more leakage inductance. Copper or aluminum would be similar if not packed tightly.
Click to expand...
 
42OhmsPA said:
You kinda lost me, I need to read it about 6 more times. ?

If I'm understanding, you're saying wiring 230 EU inverters to each primary would work nicely for US 120/240 output?
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I'm still learning about magnetics. It is almost a lost art (some of the more obscure aspects and applications.)
On-grid power transformers are mainstream, but optimized for cost.

Two separate issues. You can use a 230V inverter with isolation transformer to create 120/240V split phase. That derives a new neutral, which you bond to ground.
You can just as well stack two 120V inverters in series (or use a split-phase inverter) and connect such a transformer so 100% of inverter power is available on either 120V phase or 240V phase.

Second issue is that real transformers you purchase aren't like the idea or near-ideal ones you may have studied.
We expect, with sine wave voltage applied, to get a small sine wave current under no-load (shifted +90 degrees because it is an inductor).

What I find is relatively high current, like 4A (480VA for a 240V input), under no load.
The current looks more like a Hersey's kiss than a sine wave. That is something called "saturation", the no-load current is enough to almost make the iron core stop working, and current shoots up high.

A transformer optimized for this application (maybe twice as big) would behave nicely. You should be able to find and buy one, if you try hard enough and understand the specs.

What I've done is to operate transformers well below their rated voltage. They are much closer to ideal that way. Like draw maybe 0.6A instead of 4.0A, and make a rounded curve on the oscilloscope.
 
Thank you @Hedges I'm going to do some more homework on the neutral and grounding as well as understanding what can happen if a fault would occur.

If I went this route I would definitely oversize.
 
This sounds like an even more modular route, and totally different direction than the point of an AIO. And of course totally not against it. I think it's fascinating all the options.
 
My thinking is you are still gaining the features of an aio but utilizing the transformer to optimize, I also think the single phase units will be more robust since the countries that use them have been into renewable energy long before it took off in the US.
 
EastTexCowboy said:
I've been watching. It looks like they may have solved the feeding back to grid issue with a firmware update. We'll see. I'm pretty sure I'm not doing anything until this fall at the earliest, and maybe next spring. If it's the 18kpv I want to see some more track record. If it's something else - well, I haven't found a something else yet that really gets me fired up. Who knows, it may end up being four of the SCCs. I feel fortunate that I'm in a place where my system works well enough that I can wait.
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You should purchase one, they might have a slightly used one coming in. https://diysolarforum.com/threads/t...eturning-and-replaced-with-sol-ark-15k.66786/

History repeats itself: https://diysolarforum.com/threads/i...ipment-whats-good-at-tier-2.65062/post-817667

I lost 100 hours plus working for Signature Solar for free. 100 hours I could have spent fishing, drinking, quality time with The Official Loads Tester, cruising, traveling.............

I like the EG4 MPPT100-48HV but I don't think I'd purchase another inverter there unless it has a very long track record. I doubt that will happen, when this blows up they will move on to another OE manufacturer.
 
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