Low Frequency Vs. High Frequency Inverters

[@curtchase3730]

One reason the low freq inverter is "better" for heavy inductive loads is that the big heavy power transformer, being a huge ball of wire, is nearly indestructible from a short overload. If the device trying to start ( ie: air conditioner, table saw, freezer, etc.) approaches the output limit of the inverter, a voltage sag will be the result and a trip condition may result. A hi freq inverter, when subjected to a similar load, will try it's hardest to fight off the surge and make the device happy while actually failing and blowing up all it's MOSFETS trying! No different than vacuum tube circuits VS transistor counter parts!

[@jimmurphy5355]

Yeah, but no. I have designed AC power conditioning and regulating products, and the transformer in "Low Frequency" inverters is NOT what gives them the ability to handle surges. In general, low frequency inverters do handle surges better, but the reason is because the number and ratings of the FETs driving the big transformer. I don't know WHY the designers of high frequency inverters skimp in that area, but if they didn't, it would be totally practical to make one that had just as much surge cpapacity as a low frequency inverter.

[@xtneuron]

Any high frequency inverter that self destruct when overloaded was poorly designed. A low frequency inverter will equally be damaged if the power switch rating is exceeded. Sturdier designs always have current limiting circuits.

[@curtchase3730]

@@xtneuron Thanks for the info! Yes, makes sense. I figured a low freq inverter would have fewer parts to fail, but I guess not. I agree that just about all budget Chinese hi freq inverters are designed to just barely hit specs but cheaply. They allow no room for any overloading. They also have piss poor isolation and RFI suppression. Some are so bad that even the neutral leg is floating and if it is bonded to ground...POOF!

[@quickquote1568]

@@jimmurphy5355 Uh... no. An iron core copper wound output transformer enhances surge capacity through a principal known as the flywheel effect, which is directly proportional to the physical amount of iron present in the transformer.

[@jimmurphy5355]

@@quickquote1568That is not true. The transformer has no such flywheel effect

[@rilosvideos877]

One important question remains open: who are low and high-frequency combined, e.g. in Victron? How do they achieve low idle consumption beeing low-freq. inverters? They combine PWM with a low-freq. transformer in the end-stage. We need to understand how this works!

[@johnsonogbu8697]

I guess they monitor the type of load connected and switch type appropriately the type to be used.

[@danielking2944]

I have several of the Growatt 5K inverters and have to use transformers to form neutral for 120v loads. The transformer adds a bit of boost when starting inductive loads although that wasn’t the original purpose. I’m running two 18000BTU mini split heat pumps on one and am planning to add a third. Because of the inverter design of the heat pumps they don’t seem to have any start up surge. This particular inverter doesn’t need a transformer because the heat pumps are 240v.

[@cleversolarpower]

Good to know, thanks for sharing!

[@E9_G]

Now that we have inverter washing machines, inverter pressing irons, inverter air-conditioners, inverter fridges and freezers, isn't the concern regarding surges becoming baseless by the day? All the aforementioned devices I own are all inverter devices so I am more inclined towards the cheaper High Frequency option. Is there not enough rational in my thinking?

[@Madsci-zy8wm]

No because the inverters in the devices that you mentioned are inductive loads.

[@E9_G]

​@@Madsci-zy8wmSo are you saying that it is inconsequential despite the fact these devices are of inverter type as opposed to the traditional type? Did you understand what I meant by inverter devices, which is clearly how they are branded by their manufacturers and quite rightly so?

[@j4k3br4k3]

You are right. Back when the dinosaurs roamed the earth, we would hard start motors because the grid is an infinite power source. Now that we are going off-grid and running things off inverters, these surge currents can be a problem. Soft start circuits and "inverter drive" which is basically a VFD drastically reduce that inrush current. To give you a sense of how nasty motor starts can be. If a motor while running uses 10A, it may require 60A to kick on. Soft Starts and VFDs can drop that down to 20 to 30A surge.

[@Madsci-zy8wm]

Most people don't own inverter based appliances. And using inverter based appliances does nothing for a high frequency, inverter's well documented short life expectancy. You will have to buy at least 3 high frequency inverters over the life expectancy of a transformer based, low frequency inverter, which is one of the reasons that high frequency inverters are so cheap to purchase. They simply don't last as long as a low frequency inverter.

[@jimmurphy5355]

@@Madsci-zy8wm Pure sine wave "low frequency" inverters are high frequency inverters with a low output voltage, with the low voltage stepped up via a mains frequency transformer. The circuits that do the conversion from DC to AC in the two types are fundamentally identical, just operating at different voltages. A properly designed high frequency inverter can last just as long as a low frequency inverter - and it will cost almost as much too. But it will be more efficient, lighter, and have lower idle losses. The inverter built into a Tesla PowerWall is a high frequency type. It has fantastic surge capacity and a very long warranty. The differences in performance between low and high frequency inverters you see are due to factors other than the presence or absence of a low frequency transformer.

[@quickquote1568]

Excellent video on the difference between high and low frequency inverters. Low frequency make a much better choice for real world use.

[@jimmurphy5355]

A good quality high frequency inverter is actually the better choice in many cases. Lighter, less expensive, more efficient and lower idle dissipation. About the only definitive advantage a low frequency inverter has is its ability to be an energy sink on the AC side. That is a compelling advantage if you need that ability - typically to work with an existing solar system that has only AC output. Look up "AC coupled" solar battery back up for the details. Cheap high frequency inverters can't handle extreme surges - but you can fix that by simply using a higher capacity inverter. A high frequency inverter rated for 4 kW will handle the same start up loads as a typical low frequency inverter of half that continuous rating. And it will still be cheaper, lighter, and more efficient.

[@quickquote1568]

@@jimmurphy5355 Why do you think they're so much less expensive than a low frequency inverter? For decades, they've been considered a "poor man's" inverter because without an output transformer to provide galvanic isolation between their DC boost stage and their AC output, they have a tendency to damage AC appliances during a catastrophic failure of their H-Bridge circuit. They're simply not worth the savings in cost.

[@quickquote1568]

@@jimmurphy5355 A high frequency, output transformerless inverter is never a good choice for any residential application. The reason for this is without a transformer, they offer absolutely no galvanic isolation between their DC boost stage and their AC output which can not only damage your AC appliances but can also set an AC appliance on fire during a catastrophic failure of the inverter's H-Bridge circuit.

[@dustydawson8977]

​@jimmurphy5355 That is true, 4kw HF will handle the same start up load of 2000w LF,but it won't do it as long,That LF unit will still be running when the 4kw HF shits the bed,because there not designed to take the high surge over and over, even when over compensating, the chips will last longer but they will die, then your left with an expensive, although cheaper, paper weight,because it won't be repaired, it's just not cost effective. But if you know,design, and can do better than China man in HF, you would be a billionaire. But your not!

[@adon8672]

Apart from Victron, which other company makes low (or hybrid low-high) frequency inverter with little idle power consumption?

[@ricky786]

Studer Innotec... @StuderInnotec

[@adon8672]

@@ricky786 Great. Thank you for the suggestion.

[@Hikebike365]

Thanks for this. I'm setting up a solar emergency system for prolonged outages but not regular use. I have a have h freq giandel 600w that I bought 2 years ago and tried on our basement tv. It's an old plasma. The wattage goes from 150 to 300 depending o on screen brightness. For some unexplained reason the inverters fan will not come on. So I bought a Victron 500w thinking it'll be bulletproof....... It won't power the TV. Relays in both the TV and the inverter click on and off but it will not power the TV. Very confusing and not sure what to do. I think it's because it's a non linear load? I kinda understand the concept. What's a good hi freq inverter brand?

[@cleversolarpower]

The victron should power the load no problem. Does the inverter power other loads? is there a voltage at the output? is it an inverter/charger? Reply to my email because I won't see your reply on here.

[@Hikebike365]

@@cleversolarpower thanks for the reply. I don't see your email address? So replying here. Yes the 500w victron Phoenix Powers the heater. It won't power the TV. In eco or ON mode. Not even a flicker. Ceramic heater no problem.

[@lawrencedavidson6195]

Thanks for this useful information. Greetings from an amateur solar hobbyist in Jamaica.

[@cleversolarpower]

Thanks for watching!

[@jimmurphy5355]

"Pure sine wave" Low frequency inverters are now the most common type. Just like high frequency inverters, they use FETs to synthesize a sine wave by using pulse width modulation. They have exactly the same electronics complexity as a high frequency inverter. Both low and high frquency inverters switch their FETs at very high frequency, so the term "low frequency" can be a bit misleading. The real difference is that high frequency inverters use a DC-DC boost converter to create ~350 volts DC, and then use FETs to switch that high voltage on and off very rapidly to create the 120/240 VAC. Pure sine Low frequency inverters use high speed FET switches to rapidly turn the battery voltage on and off to create a low voltage 50/60 Hz sine wave. That low voltage sine wave is stepped up with the large, heavy low voltage 50/60 Hz transformer/

[@cleversolarpower]

Indeed, I didn't put this in the video because people would fall asleep 😀. The term "low frequency" in inverters can indeed be misleading. While low frequency inverters do use FETs that switch at high frequencies, the key difference lies in how they convert and manage power.

[@jimmurphy5355]

@@cleversolarpower Low frequency inverters also have another capability that most high frequency inverters lack: They can absorb AC power on the output side, and feed that power backwards through all the inverter circuits and charge the battery. This means that a low frequncy inverter can act like the grid. If you have an existing solar system that is grid connected, and is has only AC output, perhaps because it is built with microinverters under each panel, it will shut down when the grid fails. If you add a battery and a high frequency inverter to such a site, the solar panels are still useless. They can't charge your battery. But if you add a battery and low frequncy inverter, the AC power from your solar system can flow backwards through the inverter and charge your battery. For anyone who dove this deep into the comments - look up "AC coupled solar backup" for the details. For me, this feature of low frequency inverters was the key factor that made that type mandatory for my situation. I had a large grid-tied solar system at my house, and wanted to add a backup system that would enable that system to work even when the grid was down. So I added a 5 kW low frequency inverter, and it does exactly that. The solar system "sees" it as a grid, and fires back up, and pushes its output to the inverter, which accepts it, just like the real grid would.

[@jimmurphy5355]

@@s.mendez7160 I have no idea. That would be a question for Victron tech support.

[@quickquote1568]

High frequency inverters use a far more complex design and have a much higher parts count which makes them more difficult and costly to repair. We charge a higher total when quoting a high frequency inverter repair due to a longer diagnosis and repair time.

[@jimmurphy5355]

@@quickquote1568 If you are talking about a simple low frequency inverter that switches the DC from the battery at the mains frequency, and produces a rectangular wave output, I agree. That type of inverter has a very low parts count. On the other hand, a pure sine wave low frequency inverter has a circuit complexity that is comparable to a high frequency inverter It matters very much what kind of low frequency inverter you are comparing.

[@AnonJohn143]

Informative and helpful. Thanks as always mate.

[@cleversolarpower]

My pleasure!

[@KerbyDaFrog]

Ty for the info!

[@isettech]

Not mentioned is the harmonic content. Many of the new high frequency inverters are true sine wave output.

[@johnx983]

High frequency inverters have problems with inductive loads and load balancing. So if you have more loads on one 120v leg or you run a power saw, these inverters can shut down on you. So you end up having to over-size your system to compensate and end up paying 10x as much, as compared to a low frequency inverter. It’s annoying that we don’t see any all-in-one outdoor rated low frequency inverters on the market, and it seems when manufacturers address that, they move to high frequency models, which will have the same issue with load balancing and induction.

[@cleversolarpower]

I wouldn't say 10x as much , but i get your point. Victron has one unit called easysolar, but the charge controller and inverter/charger is still separate. Modularity is not a bad thing.

[@bentheguru4986]

The biggest restriction is the battery config you have, fine if you are on 12, 24 or 48V, screwed on anything else.

[@samueladitya1729]

will High Frequency hybrid inverter last if the load is light inductive loads, like 0.5 hp water pump or 1hp Air conditioner using a 5kw rated hybrid inverter, If the surge load is assumed 5 times the rated load that will be 3.7kw at most, and that is still smaller than the power rating of the inverter it will last right?

[@cleversolarpower]

Of course.

[@Kosmonooit]

Victron all the way! Although not the cheapest but an excellent product

[@cleversolarpower]

Yeah, it's reliable.

[@john0270]

Other than my chicom inverter handles my microwave, space heater, coffee pot , vacuum cleaner, grinders, saws, fridge, freezer, window ac ect ect ect.... where as the double the price victron phoenix 1200....... not a chance. Charge controllers seem to be great though, super flexible/programmable.... have 6 of them 😂

[@majharulislam5950]

Low frequency Inverters at no load may have mechanism to isolate the Iron core transformer to minimize the core loss. But in run time it will be in line and this core loss will be significant compared to high frequency Inverters. On the otherhand, as Iron core have large voltage regulation at over load condition during surge power, hence limiting primary side current of iron core transformer through FETs. Ultimately, can take care of any high torque inductive load in the starting time without damaging inverter ckts.

[@cleversolarpower]

Thanks for your comment! I did not know that.

[@sleepingbear6116]

Thanks very informative 👍👍👊👊

[@cleversolarpower]

Thanks! Glad it helped.

[@henkmeiring01]

Three years back i was sceptical about high freq inverters.That is why i bought four and two sets of lead acid batteries .Two inverters per battery pack .For breakdown reasons.So far no problems.A friend of mine have one that is in its sixth year.And its very cheap.Prices between 200 and 400 dollars each.Depending what type of built in charger it have.If i convert South African money to dollar. But both of us avoid microwaves,electric stoves,toasters.Cant utilize it anyway because of low battery capacity.And batteries extremely expensive.

[@cleversolarpower]

If your loads are low compared to the power rating of the inverter, then that will also extend the lifespan. Maybe thats happening in your case. They can last up to 10 years as well.

[@MarkSpohr]

How does a high frequency inverter make 50 or 60 Hz AC ?

[@cleversolarpower]

The MOSFETs switch very fast to create a sine wave. That's why it's called high frequency. Imagine a modified sine wave with the visible steps in between. MOSFETs in a pure sine wave high frequency recreate a sine wave by switching very fast.

[@MarkSpohr]

@@cleversolarpower Thank you

[@adon8672]

Why are the vast majority of inverters these days (including off-grid, Grid-tied, hybrid and even industrial inverters) of the high frequency type? Could it be that longevity isn't that big of an issue afterall?

[@NigelM18]

Longevity is never a priority for any electronic device made today. They want it to break so you have to buy another one.

[@cleversolarpower]

Grid tie is low frequency. They should last you about 10years. That's the standard warranty period in Belgium. The reason they last so long is that they don't have to supply surge power because the grid takes the surge demand. Off grid is less forgiving. Imagine you are on a boat and your inverter fails. Dependability becomes more of a factor then.

[@albertorodas6479]

For fish farming you need 365/24/7 availability air supply.

[@seymourpro6097]

Shipping weight rules! Shipping from China is always priced according to the weight of the container.

[@adon8672]

@@seymourpro6097 I beg to differ. In shipping, volume is more important of a greater concern than weight. Shipping weight also doesn't explain why even US based manufacturers like midnight solar are gravitating towards HF inverters.

[@brushbum7508]

Good Morning ! Thank You. TAKE CARE..

[@stephenhickman9502]

If your inverter struggles to power a microwave oven, it's likely an HF inverter. 😆 like mine. My inverter will run my microwave, but it stumbles at first for a few seconds.

[@scoobyblu5815]

Are you working for victron?

[@cleversolarpower]

No, but I'm a fan of their equipment. High quality, many options, good customization,...

[@eugen-m]

Big like 😉❤

[@michaelagbayani4961]

Low freq is better the idle is not that big a diff some HF has higher idle load vs low freq inverters

[@cleversolarpower]

Indeed, like i said in the video it depends on the manufacturer.

[@adon8672]

Why do low frequency inverters always have relatively high idle power consumption?

[@curtchase3730]

Most likely, the big heavy power transformer has inherent loss compared to a hi freq unit.

[@jimmurphy5355]

The large, heavy 50/60 Hz transformer has an iron core. The direction of the magnetic field in the core has to alternate at the mains frequency. That alternation induces losses in the iron - think of it as being something like friction in the alternation of the magnetic domains in the iron. These losses are directly proportional to the amount of iron, and are typically 2 watts per pound of iron. Core loss is independent of the load on the inverter.

[@adon8672]

@@jimmurphy5355 thank you for the this response. Probably the best answer to this question so far. Forgive me for asking further questions out of this answer. How's is Victron managing to keep idle consumption low, even better than many low end HF inverters? Are they somehow reinjecting the (potentially) wasted power in the iron core back into the system. I apologise if these questions sound naive but I'm really curious.

[@jimmurphy5355]

@@adon8672 I honestly don't know. The core losses can't be recovered - they heat the core, and they are gone. My best guess - and it is just a guess - they don't power the low frequency unless the load is demanding power. Some "low frequency" inverters have a power save mode that does that. Or maybe they use (expensive) ultra low loss grade iron in the core, and/or run the core at relatively low flux levels (also expensive because then you need a bigger core.) The true but not very infomative answer: better engineering and better quality components.

[@adon8672]

@@jimmurphy5355 thank you for the prompt and wonderful response. There's a lot of sense in your guesses and they are good enough for a lay person like me.

[@dustydawson8977]

Why do people keep saying low frequency inverters have high idol consumption, cheap LF inverters do, good LF inverters are extremely low idol draw. My portable low frequency 3000w continuous solar generator draws less than 13w @ idol. And you said your self you recommend victron LF inverter for its low idol consumption. Mine is not a victron, but victron is very good. Quality is the factor in low idol consumption, and you would be very hard pressed to find a HF inverter with a 13w idol draw

[@cleversolarpower]

Indeed, quality low frequency inverters don't draw as much. But you are going to pay for it. Victron says they use a hybrid system (whatever that means). There are low frequency inverters who consume way more than high frequency inverter though.

[@deadgamer9808]

In india high frequency inverters are much more expensive approximately twice as expensive

[@cleversolarpower]

Maybe there is a high import tariff going on?

[@deadgamer9808]

@@cleversolarpower yes but i think its also due to lots of indian companies manufacture low frequency inverters and they are not importing it nor they are making them ( maybe because they have to set up new plant for it also they have to discontinue their existing plants which will be not be good for business) and the one who are importing them are charging premium

[@yannickbouhier9951]

my growatt invrerter die after 3 month ; it cannot support the 35 degree of philippines !!!!!

[@cleversolarpower]

It could also be that it ran inductive loads which puts stress on the MOSFETs. 35 degrees Celcius is not that high for electronics when it's well ventilated.

[@henkmeiring01]

​@@cleversolarpowerYou are right.In summer we regularly hit 45 degrees.And my 3kw /24v inverter keeps running.With hosehold items like fans,fridge,freezer,tv.And 600w water pump.Reaching 1000w all together.Most likely problem for breakdown is when you utilize over 2kw all the time.

[@TechnoEveryday]

❤🎉❤🎉❤🎉❤

[@scoobyblu5815]

For two years non-stop my high frequency 5000 watt inverter powers my whole house and makes my hot water and it was cheap as f...I You need to redo the video 🤔

[@cleversolarpower]

2 years is nothing though. Heating water is a resistive load, so no surge power is required.

[@s.mendez7160]

@@cleversolarpower Do you think if you added "Soft Start" to an RV Air Conditioning unit which would reduce the inrush current, you could still use a High-Frequency inverter, and not stress the MOSFET's?