High Frequency vs. Low Frequency Inverter - Does it matter??

[Hedges]

My dozen Sunny Island are MINE! ALL MINE!
Also my 20 sunny boys and 2 Sunny Island Chargers.

I have 7 SI running, plan 2 more for my new house. Could loan one to my sister. Considered power for my mountain property but they might grow legs. Spares is good (and with 4x in one system, that's a couple hot spares.)

That used one for $1200 matches lowed price I paid (for new in the box.)
From DC Solar auction, I think some people bought (5048 or 6048?) for $600 or less.
When $5750 MSRP, $4750 street price Sunny Islands were all over eBay for $1700, some people said, "But I can get a Growatt for $1200!

Main limitation of Sunny Island is it doesn't have peak shave and time shift features (although it can do some time based connect to generator or grid.) Also doesn't have latest required features so not allowed as an exporting inverter for new net-metering installs, just a UPS/island grid.

But I think it is among the best battery inverters for medium to large installs. At the smaller end, for off-grid, 1x SI and an auto-transformer to make 120/240V split phase would support 12kW of Sunny Boy. Add DC coupled PV with communication or a shunt, if desired.

 

[OffGridForGood]

My dozen Sunny Island are MINE! ALL MINE!
Also my 20 sunny boys and 2 Sunny Island Chargers.

No wonder the prices stay high on these!
I sure like the SMA build quality, the price for a new one in my market in 2021 was over $5,000 so I passed and bought the first MPP 6048 as a toy/pet project (that grew) LOL. Really I just wanted better emergency lights in the shop for power outages! Well that is where this addiction hobby started. Now I have this 'on site power plant', that supplies my business electrical needs 100% 24/7 and most of my home (next door) and we use an EV for any excess during summer.
With the third MPP unit installed, we are at our production limit of 19.6kW, but this is not top tier equipment, so we target 16kW as max other than starting currents.
I feel we will outgrow the 16kW limit, and I am looking at options for 24kW, and higher quality equipment, with lower idle consumption.
My ideal solution would be a 24kW unit (pair of 12kW) with 100W or less idle, about $8,000USD range price point. A lot of bells and whistles are not needed. I have about two years for planning, see what the market does. The EG4 18kpv caught my eye. Would like to see what else comes along.

 

[solar8484]

The Genetry Solar 12 kW idles at about 30 watts unloaded. There's a generally negative opinion about them, and in dealing with them I'd say it's earned. But not for the inverter. The inverter is 100% tank. Super solid machine and way under priced.

I think the jury is still out regarding the GS inverters as there are reports that they can't run some loads like certain washing machines. Also, they use aluminum transformer windings to reduce weight but I wonder about the durability vs copper.

 

[Hedges]

"12,000W
Split Phase: 240v @ 50A (or 120v @ 50A from both L1-N and L2-N)
Single Phase: not supported. (The transformer can physically do 120v
single-phase, but none of the AC output circuitry is rated for 100A)NOTE: Inverter alarms are based on amperage, not wattage"

OK, how much 120V single phase current CAN it do?
Oh, I think it means 50A on L1, 50A on L2, 50A on N.
Surge wattage may be available at 120V (double current), but steady state 6000W not 12000W on one phase.

But I think 36kW surge into transformer means 120V at 300A, enough to start a 7kW 120V induction motor (assuming 1 second or longer surge is delivered.)

That should handle everything that ought to be on 120V and more.

Sunny Island, 11kW surge available at 120V (unless you parallel two.)

I think the jury is still out regarding the GS inverters as there are reports that they can't run some loads like certain washing machines. Also, they use aluminum transformer windings to reduce weight but I wonder about the durability vs copper.

Aluminum is the norm in transformers for use on grid above about 10kW.
Problem is if aluminum overheats, but transformers are designed to run up to about 200C. An inverter has better chance to monitor and shut down, vs. something only protected by a breaker.

I get copper when I can.

 

[OffGridForGood]

I think the jury is still out regarding the GS inverters as there are reports that they can't run some loads like certain washing machines.

A washing machine is a pretty light load in my world, the Dryer on the other had, yeah, nothing like starting up a 120v motor and a 240v heating element simultaneously...only my big air compressor is more demanding than the Dryer. In fact I pay attention to avoid cycling the compressor and the dryer at the same time if possible.
If the GS inverters have trouble with the washing machines, I wonder if that issue is about how 'clean' the power is for the electronics, rather than the total load involved. That seems like a big red flag to me.

 

[solar8484]

Problem is if aluminum overheats, but transformers are designed to run up to about 200C.

They put in extra fans to help cooling but that means the unit can sound like a jet engine. I doubt the transformer windings are rated for 200C. Thermal cycling mechanical failure risk for aluminum windings seems higher to me.

 

[CoolWill]

Genetry Solar 12KW Inverter – Genetry Solar

www.genetrysolar.com

"12,000W
Split Phase: 240v @ 50A (or 120v @ 50A from both L1-N and L2-N)
Single Phase: not supported. (The transformer can physically do 120v
single-phase, but none of the AC output circuitry is rated for 100A)NOTE: Inverter alarms are based on amperage, not wattage"

OK, how much 120V single phase current CAN it do?
Oh, I think it means 50A on L1, 50A on L2, 50A on N.
Surge wattage may be available at 120V (double current), but steady state 6000W not 12000W on one phase.

"

Transfer Efficiency	99% (yeah, the competition always lists this useless spec!)
AC Charge Efficiency	~72% (wonder why the competition never lists this!)
Maximum Charge Current	approx. 120A @ 48v

"

120A x 48V x (1 - 72%) = 1612W dissipated by inverter when charging?
72% is more like expected round-trip efficiency with lead-acid battery.

The way I understand the design, 60 amps is the rated limit for the wiring and contactors.

 

[Hedges]

Sure, and 50 or 60A rated conductors can handle about 250 or 300A for a while.

Contactors could be the most vulnerable. Problem is if they close and bounce into such a load, because they pull an ark and then fall into a molten pool of metal. If already closed when a switch elsewhere applies the load, not so bad.

A 60A breaker will magnetic fast-trip in about 8 milliseconds at 300A, so it disconnects for short circuit.
Anything less than that and thermal (or magnetic-hydraulic) will wait a while before tripping.
Maybe 15 minutes at 150%, a few minutes to seconds at 250% to 450%.

You can run a 15A 1800W 120V induction motor (e.g. air compressor) off a 15A outlet, which may have 15A or 20A breaker. The starting surge is about 75A, but typically less than a second.

Copper has thermal mass, and an impulse of thermal energy doesn't raise temperature much.

Does Gentry have its output going through any contactors?
Sunny Island only would for external load-shed contactors. Internally it has that for grid input (and can attempt to invert from battery to limit input current, not sure how fast it enables.)

Sunny Island is rated 5750W continuous at room temperature, 11,000W 3 second surge (just under 100A), 180A surge for 30 milliseconds (just long enough to fast trip a breaker; I would think 30A but manual says not over 20A breaker would be sure to trip.) For Gentry at twice the wattage rating to deliver 300A for some amount of time is in the same ballpark, and maybe it can be sustained long enough for motor starting.

 

[CoolWill]

Sure, and 50 or 60A rated conductors can handle about 250 or 300A for a while.

Contactors could be the most vulnerable. Problem is if they close and bounce into such a load, because they pull an ark and then fall into a molten pool of metal. If already closed when a switch elsewhere applies the load, not so bad.

A 60A breaker will magnetic fast-trip in about 8 milliseconds at 300A, so it disconnects for short circuit.
Anything less than that and thermal (or magnetic-hydraulic) will wait a while before tripping.
Maybe 15 minutes at 150%, a few minutes to seconds at 250% to 450%.

You can run a 15A 1800W 120V induction motor (e.g. air compressor) off a 15A outlet, which may have 15A or 20A breaker. The starting surge is about 75A, but typically less than a second.

Copper has thermal mass, and an impulse of thermal energy doesn't raise temperature much.

Does Gentry have its output going through any contactors?
Sunny Island only would for external load-shed contactors. Internally it has that for grid input (and can attempt to invert from battery to limit input current, not sure how fast it enables.)

Sunny Island is rated 5750W continuous at room temperature, 11,000W 3 second surge (just under 100A), 180A surge for 30 milliseconds (just long enough to fast trip a breaker; I would think 30A but manual says not over 20A breaker would be sure to trip.) For Gentry at twice the wattage rating to deliver 300A for some amount of time is in the same ballpark, and maybe it can be sustained long enough for motor starting.

The Genetry output doesn't go through a contactor. But there is a contactor for grid/generator input. It will do 12 kW all day and 18 kW for as long as you can keep the toroid and FET temps below 110F, I think. It has 4 monster Delta fans that sound like a large drone lifting off when they go full blast. It will do 36 kW for maybe 3 seconds before shutdown.

 

[CoolWill]

I think the jury is still out regarding the GS inverters as there are reports that they can't run some loads like certain washing machines. Also, they use aluminum transformer windings to reduce weight but I wonder about the durability vs copper.

I think a revision or so back that was a problem. It seems they have straightened that out. It runs every single thing I've thrown at it well into overload.

 

[solar8484]

It will do 12 kW all day and 18 kW for as long as you can keep the toroid and FET temps below 110F,

110F FET temp? That's very low. Perhaps 110C?

 

[CoolWill]

110F FET temp? That's very low. Perhaps 110C?

I think 110F is the low cut in point.

 

[solar8484]

I think a revision or so back that was a problem. It seems they have straightened that out.

Apparently not, https://www.genetrysolar.com/community/postid/40221/

 

[CoolWill]

Apparently not, https://www.genetrysolar.com/community/postid/40221/

There may be a problem, but I wouldn't rely on what that guy says. If you follow his posts, he's got the most insane rigged up mess of a system. He just blew up his two inverters by accidentally switching them into the grid. At any rate, I have no complaints about how the GS inverters are operating with many different loads I've put on them.

 

[Techie007]

The Genetry Solar 12 kW idles at about 30 watts unloaded. There's a generally negative opinion about them, and in dealing with them I'd say it's earned. But not for the inverter. The inverter is 100% tank. Super solid machine and way under priced.

Interesting - I looked them up, Genetrysolar.com they spec the 12kW LF at 48W idle consumption - impressive for a 12k LF. I notice they offer the 12k in various voltage (customer can choose) 24, 36, 48 60 (TBD) - I don't think I can even imagine a 12k running 24v - likely they derate the output to hold the amperage to acceptable levels. Interesting to see 36-volt. They say US assembly.

I have one of their 6kW units, and in real life it too idles under the advertised 24w at around 19w. I don't know of any inverter currently on the market that comes close to this low of an idle current at this high of an output while also maintaining a 3x surge ratio.
Their 12kW inverter can in fact do 12kW at 24v if your batteries and wiring can handle the current without dropping too much voltage, but you do lose surge capacity due to increased FET currents (they say it can do 28kW at 24v instead of the full 36kW).

I think the jury is still out regarding the GS inverters as there are reports that they can't run some loads like certain washing machines. Also, they use aluminum transformer windings to reduce weight but I wonder about the durability vs copper.

The reported issues with washing machine is due to the fact that some of these washing machines tear up the AC line with lots of pulses, half-wave draw, wave-skipping, and other chopping measures that cause noise and voltage regulation issues for their 6kW inverter (mainly due to transformer winding resistance) that eventually cause the washing machine to abort cycle. They added some additional output filtering early on that helped with the noise at the expense of increasing idle consumption slightly, but the regulation issues remain tricky because it's only adjusting the output voltage 120x/second (like a lot of other low frequency inverters, on each half-wave). IIRC, one of their customers who had this issue upgraded to their 12kW inverter when it became available, and thanks to the significantly lower transformer winding resistance, the output was much more stable under this type load and their washing machine no longer had any issues. This is because inverter's voltage regulation is only needed to compensate for fluctuating input voltages and voltage drop inside the transformer caused by load. Anything that reduces either of these points results in less reaction needed from the (slow) voltage regulation logic, and thus a more stable and less distorted output under these transient loads. Something to note is that these type loads will be a crapshoot with any small inverter; some do very well (to everyone's surprise in some cases), some struggle along (like the GS 6k and likely many others), and some fail entirely and power off/go up in smoke under this type load (like some cheap HF inverters).

The way I understand the design, 60 amps is the rated limit for the wiring and contactors.

The Genetry output doesn't go through a contactor. But there is a contactor for grid/generator input. It will do 12 kW all day and 18 kW for as long as you can keep the toroid and FET temps below 110F, I think. It has 4 monster Delta fans that sound like a large drone lifting off when they go full blast. It will do 36 kW for maybe 3 seconds before shutdown.

The limit is for the AC output wiring, connectors (output terminals), and the input relays. With all the forced moving air inside the inverter, it could probably handle over twice that much under sustained load. However, the fans spin up when the FETs and transformer get hot, which could take minutes—long after wiring would get hot (which would be a matter of seconds, which is the main reason peak surge is limited to 2 seconds). Internal temperatures are limited to 180°F (yeah, it's weird they use Fahrenheit instead of Celcius unlike most of the industry). I think the transformer could easily handle more and have asked them repeatedly to increase its maximum to 100°C (212°F) while reducing the FETs to 80°C (176°F). Output is wired directly to the transformer and does not go through relays; it is the input (for charging/passthrough use) that is bridged to the output by two relays (one is a disconnect, and the other auto-selects between 120/240v input, mainly for camper use).

I've put over 10,000 kWh through my Genetry Solar 6k inverter so far, and it's still going strong!

 

[NevadAdobe]

Maybe watch the YT video before stating that Sol-Ark is the "Top of the Top"

That is the video that absolutely changed my mind in regard to AIO... just not even dispute-able... liars figure but figures never lie. I just wish that we had ordered a 6,000 watt Conext SW or XW Pro prior to having a technician say that an SW4048 would be able to parallel to grow our off grid electrical system. Shoulda, coulda, woulda...my bad!

 

[niktak11]

That is the video that absolutely changed my mind in regard to AIO... just not even dispute-able... liars figure but figures never lie. I just wish that we had ordered a 6,000 watt Conext SW or XW Pro prior to having a technician say that an SW4048 would be able to parallel to grow our off grid electrical system. Shoulda, coulda, woulda...my bad!

There's too bad considering that this video gets called out all the time for being completely misleading

 

[1201]

There's too bad considering that this video gets called out all the time for being completely misleading

How?

 

[niktak11]

How?

He purposely overloads one leg beyond what the spec sheet says is the max. Try that same test on an EG4 18kPV or a sol-ark 15k. Both of them will be able to start TWO of those compressors simultaneously and the latter would be able to do it while also running a large central heat pump (while also costing a fraction of the equivalent Schneider system).