actual capacity of an inverter

[Brett V]

I do find it pretty disingenuous to play word games with the ratings. For the most part, people who are buying and using this equipment are knowledgeable enough to understand what they need. Just publish actual specs and let the buyer decide.

 

[rogerdw]

The inherent, instant bi-directional power flow change capability also make LF inverters much better choice for AC coupling of PV GT inverters.

Unfortunately most of your post goes over my head, but this bit stood out.

Can you expand on it a little more please?

 

[AntronX]

I don't know why you are tagging EG4 guys, all of their current inverters will kickstart any motor just fine.

6000xp craps out when starting a chop saw while my 800 watt victron could run it.

 

[SunDave]

that or like everything that comes out of china its a lie and its not a 12k or even an 8k inverter inside of the case but lets be kind and call it a crappy 2kw inverter. and that would be closed to the truth.

I understand your dislike for other brands than yours, but this month there was a day I ran a Sol-Ark that inverted over 12kW of DC to AC for 2 hours and 18 minutes straight. I checked solar assistant. So it's just a bit of stretch to call it 2kW.

 

[RCinFLA]

Unfortunately most of your post goes over my head, but this bit stood out.

Can you expand on it a little more please?

You asked for it.

The sinewave PWM H-bridge on LF inverters is on primary side of heavy silicon-iron LF transformer. If secondary AC side transformer instantly changes from a load to a source (in sync) like when AC coupling, the PWM H-bridge, without missing a beat, will turn into rectification of the pushed back feed AC power creating DC charge push into batteries.

Only difference between AC inverting, battery charging, back feeding grid, limiting AC input draw current, or supplementing AC output is just a slight tweak to H-bridge PWM duty cycling to make the AC sinewave output of LF transformer be a little more or a little less than AC input voltage.

This is all controlled via AC current measurements on the three connection AC node.

HF inverter is more complicated with more semiconductors, but less cost and much less weight. It steps up battery voltage to high voltage DC. There is a high frequency ferrite transformer that has a high frequency primary side H-bridge made of MOSFETs and secondary side synchronous rectification H-bridge made with insulated gate bipolar power transistors for high voltage DC. There is an output L-C filter similar to a buck DC to DC converter that integrates the variable duty cycle high voltage pulses to HV DC, about 500vdc for 230 vac inverters, about 250vdc for 120vac inverters.

Finally, there is a third H-bridge made of insulted gate bipolar power transistors that chops up the HV DC via a PWM, sinewave shaped variable duty cycle followed by L-C filter to create the inverter's sinewave AC output.

It is the HV DC inductor filter that causes the switch over time delay issue on HF inverters to switch from sourcing to AC PWM inverter or reverse direction to charge battery from HV DC node. The energy stored in the inductor must be flushed before power flow direction can be reversed.

Solar charge controller feeds the HV DC node. Sinewave output H-bridge also can rectify the AC input to produce HV DC for battery charging from grid or generator.

It is a bit more complicated to explain why HF inverters often have issues with high surge current load,, but it has to do with the HV DC filter capacitors having very little energy storage so supply surge and/or the battery to HV DC converter not having the peak power overhead capable ferrite transformer. If ferrite transformer saturates due to peak load surge it can blow out the primary side MOSFET's.

 

[AntronX]

@RCinFLA did you create this HF inverter drawing? It's so dense with clutter it makes my head hurt. I cleaned it up some.

 

[SunDave]

Not my specialty so I can't absorb it all, but I appreciate the info from both of you. Took me a little while into the solar journey to figure out how the grid tied setups work, and that the units just tweak the voltage up and down to "push" or "pull" power. That's how I look at it anyhow.

 

[Daddy Tanuki]

I understand your dislike for other brands than yours, but this month there was a day I ran a Sol-Ark that inverted over 12kW of DC to AC for 2 hours and 18 minutes straight. I checked solar assistant. So it's just a bit of stretch to call it 2kW.

its not so much my brand as it is topography. if an inverter claims 5kw it should be able to do what a 5kw circuit on a house does... IE about 15-20 amps including the ability to surge start anything that you could start in your wall socket. everyone jumped on them (HF) as they were at the time cheaper, but in order to get the same real capacity which can be anything from a well pump to a chop saw to a compressor to anyhting you would normally plug into a circuit then they are sorely over rated and its essentially a lie in my opinion. your opinion may be different but if it can't do what a 2kw inverter does then its not truly a 8kw or 12 kw or however they want to advertise it to drag in the suckers....

when you pay 2.5k for a 4.4kw inverter or you could pay 1.6k for a supposedly 12kw inverter most people being cheap will jump on the larger number. but in reality is it larger? I think not. under perfect conditions with a yuge battery and oversized cables and lightening hitting the output side it might make nameplate... but even then its doubtful to me.

so 5kw at 240 is about 20 amps and the same 5kw at 120 is about 40 give or take if you cant start a chop saw on a 20 amp circuit there is something amiss. call it what you want but a 5kw generator can start that chop saw.... a 15 amp circuit in the house can start the chop saw, but the 12.... i meant mis-labled 8kw unit cannot.... Oh it was a mistake in the programming... really? sounds like the maker knew it could not handle it regularly so they gave you a crippled POS and an excuse.

just my take on it.

 

[rogerdw]

You asked for it.

Yes I did. Wasn't expecting that much detail ... but appreciate it all the same. I'm not going to pretend I understand it all fully but the diagram certainly helps.

The reason I picked up on your comment initially was because I wasn't sure if you were suggesting LF inverters are a much better choice for AC coupling when used as PV GT inverters ...

... or when AC coupled to a PV GT inverter.

I had read comments elsewhere where it was suggested that it is best to use a LF inverter when you want to AC-couple to an existing inverter system ... so say I have an off grid inverter providing my own mini-grid and I want to add to it and AC couple another inverter ... then I should ideally choose a LF one ... or does it not matter?

I am in that situation already ... but because I only had access to a HF inverter at the time, I used that ... and it performs well enough. Maybe I'm just lucky it hasn't blown up yet.

And I'm with Antron, I'm interested to know if you created those graphics (and with what) or where they came from. Thanks.

I cleaned it up some.

That does help thanks, though "Open image in new tab" helps enormously too.

And same question, what did you use to clean it up?

Reason I ask is because I spent last evening trying to draw some basic block diagram circuits and ended up frustrated that I couldn't find vector symbols without paying a heap for them all. Ended up creating a few of my own but easier to not have to reinvent the wheel.

 

[AntronX]

I used mspaint

 

[GRMRC]

You asked for it.

The sinewave PWM H-bridge on LF inverters is on primary side of heavy silicon-iron LF transformer. If secondary AC side transformer instantly changes from a load to a source (in sync) like when AC coupling, the PWM H-bridge, without missing a beat, will turn into rectification of the pushed back feed AC power creating DC charge push into batteries.

Only difference between AC inverting, battery charging, back feeding grid, limiting AC input draw current, or supplementing AC output is just a slight tweak to H-bridge PWM duty cycling to make the AC sinewave output of LF transformer be a little more or a little less than AC input voltage.

This is all controlled via AC current measurements on the three connection AC node.
View attachment 266756
HF inverter is more complicated with more semiconductors, but less cost and much less weight. It steps up battery voltage to high voltage DC. There is a high frequency ferrite transformer that has a high frequency primary side H-bridge made of MOSFETs and secondary side synchronous rectification H-bridge made with insulated gate bipolar power transistors for high voltage DC. There is an output L-C filter similar to a buck DC to DC converter that integrates the variable duty cycle high voltage pulses to HV DC, about 500vdc for 230 vac inverters, about 250vdc for 120vac inverters.

Finally, there is a third H-bridge made of insulted gate bipolar power transistors that chops up the HV DC via a PWM, sinewave shaped variable duty cycle followed by L-C filter to create the inverter's sinewave AC output.

It is the HV DC inductor filter that causes the switch over time delay issue on HF inverters to switch from sourcing to AC PWM inverter or reverse direction to charge battery from HV DC node. The energy stored in the inductor must be flushed before power flow direction can be reversed.

Solar charge controller feeds the HV DC node. Sinewave output H-bridge also can rectify the AC input to produce HV DC for battery charging from grid or generator.

It is a bit more complicated to explain why HF inverters often have issues with high surge current load,, but it has to do with the HV DC filter capacitors having very little energy storage so supply surge and/or the battery to HV DC converter not having the peak power overhead capable ferrite transformer. If ferrite transformer saturates due to peak load surge it can blow out the primary side MOSFET's.

View attachment 266757

The Engineer in me appreciates the detail in this post. Geeks understand Geeks…

 

[Mattb4]

its not so much my brand as it is topography. if an inverter claims 5kw it should be able to do what a 5kw circuit on a house does... IE about 15-20 amps including the ability to surge start anything that you could start in your wall socket. everyone jumped on them (HF) as they were at the time cheaper, but in order to get the same real capacity which can be anything from a well pump to a chop saw to a compressor to anyhting you would normally plug into a circuit then they are sorely over rated and its essentially a lie in my opinion. your opinion may be different but if it can't do what a 2kw inverter does then its not truly a 8kw or 12 kw or however they want to advertise it to drag in the suckers....

when you pay 2.5k for a 4.4kw inverter or you could pay 1.6k for a supposedly 12kw inverter most people being cheap will jump on the larger number. but in reality is it larger? I think not. under perfect conditions with a yuge battery and oversized cables and lightening hitting the output side it might make nameplate... but even then its doubtful to me.

so 5kw at 240 is about 20 amps and the same 5kw at 120 is about 40 give or take if you cant start a chop saw on a 20 amp circuit there is something amiss. call it what you want but a 5kw generator can start that chop saw.... a 15 amp circuit in the house can start the chop saw, but the 12.... i meant mis-labled 8kw unit cannot.... Oh it was a mistake in the programming... really? sounds like the maker knew it could not handle it regularly so they gave you a crippled POS and an excuse.

just my take on it.

I am curious. Have you ran with any of the HF AIO's? My experience with both LF and HF style has me preferring the HF based on efficiency.

 

[Daddy Tanuki]

I am curious. Have you ran with any of the HF AIO's? My experience with both LF and HF style has me preferring the HF based on efficiency.

i have two sigineers but they are for a dedicated load dump and will go online next year once winter retreats and I can finish the boiler project. I chose them as they were cheep and as they are only powering a water heating element there is no issues with power factor and surge.

I understand the issues the reason I started this thread is that many do not, they hear things like LF's are dinosaurs, LF's are not efficient, etc. etc. then you read threads where the OP talks about not being able to run a chop saw on what I now understand to be an 8k inverter, or it could be two 4.5's in the same housing... still even if it is a 4.5 its the same size as my LF inverter and should start a chop saw... we are not talking a compressor with a single phase 3.5 hp motor with a broken unloader valve or something really challenging like that.

to clear the air I was running the chop saw on a 2k LF magnum. my current inverters are both 4.4k units so 8.8k paralleled and to be honest until I added the oil centrifuge I did not need the second one. thats a/c fridge, freezer and the shop and all of its various tools.

the whole thing is people bought into them (HF) due to cost, and I think they have been handed a disservice with that thought as they end up spending more to get the same real world output.

some of the newer midnite and victron with their newer topology might be able to handle more surge load than the chinesium ones but I bet they can't go as deep as a LF. i guess it depends upon what you need, but what i do see happening is legacy LF inverter companies closing as they cannot sell enough in comparison to the HF sales out fo china and when you need something that just works it is impossible to beat an old trace, xantrex, magnum or outback. they just work...

HF inverters have their place I just do not see it as a primary driver for an essential system. the dump load system as i said, I have two inverters with a supposed 10kwh between them paralleled. I half way want to wire them in place of the magnums to see how they would handle it, but they are 230 native units not 240 split phase so that would be a PITA and just for testing purposes, I have the prerequisite transformers due to my work but why?

I also have a samlex 600 watt and a xantrex 2000 watt that are both HF and they work great for what I use them for...

once again your experiences might be different from mine but I would rather turn people onto simple bullet proof units that work without all of the what I see as extra effort that is required for the HF offerings (not to mention the whole deye debacle ).

 

[seneysolar]

what i do see happening is legacy LF inverter companies closing as they cannot sell enough in comparison to the HF sales out fo china and when you need something that just works it is impossible to beat an old trace, xantrex, magnum or outback. they just work...

I have a brand new in the box Magnum 4024 PAE that im saving for a rainy day because I know at some i wont be able to get one.

 

[Mattb4]

... i guess it depends upon what you need, but what i do see happening is legacy LF inverter companies closing as they cannot sell enough in comparison to the HF sales out fo china and when you need something that just works it is impossible to beat an old trace, xantrex, magnum or outback. they just work...

...

The reasons that Trace, Xantrex, Magnum or Outback are going out of business is their refusal to change. They might "just work" but they do not work at a price point that many can afford nor have they added features to make them consumer friendly. Heck many have not adopted LiFEPO4 batteries as a norm yet. Frankly without the new features and prices of the HF inverters the solar industry would be moribund. People like myself would still be ignoring it since it was out of reach cost wise.

You might build the best mousetrap but if your competitor builds one at half the price, and works good enough most times, you will soon go out of business.

So trying to push people towards a failing legacy industry seems pointless to me.

 

[42OhmsPA]

I think it depends a lot on the brand of the equipment and the components used.
I've been running my entire house off HF for about 2.5 years now.
I haven't found a surge load it won't handle.
120V - chop / miter saws, circular saws, grinders, shop vacs, pancake compressors, etc.
240V - deep well pump and air compressor.
I've had over 80% load imbalance between legs with no issues.

If anyone is bored, there is a video here of the bigger air compressor starting when i was running a single 10KW unit before the parallel upgrade.

 

[OffGridForGood]

Frankly without the new features and prices of the HF inverters the solar industry would be moribund. People like myself would still be ignoring it since it was out of reach cost wise.

I have to agree.

I've been running my entire house off HF for about 2.5 years now.
I haven't found a surge load it won't handle.
120V - chop / miter saws, circular saws, grinders, shop vacs, pancake compressors, etc.
240V - deep well pump and air compressor.

Ditto - my business and home !
Although I didn't take the deep plunge initially - started with just one 6kW unit and one server rack - to test and see what it could do (and not do). But was impressed enough to expand, and expand. And now took the plunge to update everything, neaten it all up, plan for future further expansions. AiO's are here to stay. Honestly most of the issues members report are FW and controls, not the base equipment.

 

[timselectric]

Same here. HF running everything for 3 years.
No issues with it. Plenty of induction loads.

 

[Daddy Tanuki]

Happy new years...at least here in Japan anyways!

 

[sunsurfer]

Most chop saws use a classic brushed universal motor (AC/DC) and are series wound. Its not a capacity issue, its the inverter going into protective mode from the boat loads of reactive power. You need the ability to soak up all that grunge in a big fat transformer to smooth things out for the switching gear.

Talk about a torture test, kinda cruel making an HF try and run a chop saw. Might as well throw a vitamix 5200 full of ice on medium speed in the mix while you are doing the inverter torture testing. Make it eat electric shards of glass.

I use a chop saw for firewood production and it works very fast and easy for small to med size wood. I also use an electric chain saw when possible and it also is a brush/universal. So much nicer than a gas saw. I will ONLY use them on my big iron AIMS inverter. I won't even run them on my Victron inverters though they can handle it fine. AIMS gets to take the brunt and its a messy load for sure!

 

[AntronX]

One good thing about universal brushed motors is they can run on DC. So that's what i did - tried it with 12s NMC battery at 44v. A bit weak but workable. It even cut a 2x4. You could connect 3 solar panels in series and run it direct from solar. Just have to tape that handle switch on to avoid arc flash from destroying it.

 

[SunDave]

Nice test. Cool that you tried it. The tiny allegator clipped wire is likely a problem in itself.

 

[AntronX]

The tiny allegator clipped wire is likely a problem in itself.

Those double as fuses

 

[timselectric]

That 2x4 is rotten. lol

 

[AntronX]

That 2x4 is rotten. lol

Part 2 cutting up shipping pallet