June 19, 2019

Which is better? A “low frequency” & “high frequency” inverter?

Power inverter has two types: Low frequency and High-frequency power inverter.

off-grid inverter is simple which convert the DC power stored within a battery (direct current, 12V, 24V or 48V) into AC power (alternating current, 230-240V) that can be used to run your household items and electrical appliances, from fridges to televisions to mobile phone chargers. Inverters are an essential item for anyone without access to a mains power source, as they can easily provide a plentiful amount of electricity.

Low-frequency inverters have the advantage over high-frequency inverters in two fields: peak power capacity,  and reliability. Low-frequency inverters are designed to deal with higher power spikes for longer periods of time than high-frequency inverters.

In fact, low-frequency inverters can operate at the peak power level which is up to 300% of their nominal power level for several seconds, while high-frequency inverters can operate at 200% power level for a small fraction of a second.

The second main difference is reliability: low-frequency inverters operate using powerful transformers, which are more reliable and sturdy than the high-frequency inverter’s MOSFETs, which use electronic switching and more prone to damage, particularly at high power levels.

In addition to these qualities, low-frequency inverters come with a wide range of technical features and capabilities which most high-frequency inverters lack.

2019, News
  1. Miguel Rodriguez May 4, 2021 at 10:03 pm Reply


    How can I know if my Inverter is high or low frequency? I have a MPPsolar Hybrid SPLIT PHASE LVX SERIES – LVX6048


  2. Goodmorning sir, my name is Chinedu. My question is, is Techfine Inverters reliable for use in Africa since they are low frequency inverters.

  3. Is high frequency inverter are safe for equipments with motors like ref. & Aircons?

  4. Hi, I’m looking at growatt transformerless high frequency inverters. The rep. Who I am in communication with tells me that the 18kw inverters will peak at 54kw for 20 seconds, also has wifi, mppt, bms. I’ve been very specific with him about these inverters needing to run my house and my shop. Which includes refrigerators, freezers, A/C, water heater, stove/oven, power tools, auto lifts, well pump, welders, compressors. He guaranteed me that he has personally installed 60-80 systems using these inverters with excellent results. Including 100kw system for a mansion. He is a local business, so I know if there is a problem I can pack the inverters up and return them. I havent seen many reviews on the inverters, but I do still see many companies selling low frequency inverters with a heavy transformer.
    It seems that these transformerless inverters are relatively new. I have not made the purchase yet. I will be in about a week.
    Any help would be great. These are the growatt (blue) 3000/9000 watt transformerless high frequency inverters wired 6 in parallel. Thanks.

    • Growatt is indeed a force to reckon with in the inverter R&D world and they are quite popular and pricey too. I believe they are the third best globally, u can check that. It is transformerless with all round protection and also usually a power factor of 1. These inverters are the best money can buy so go for it. It is indeed peace of mind.

  5. Aaron, your inverter shuts down because your inverter of 3kva has a power factor of most likely 0.8%. So the watts rating of your inverter should be about 2.25kw. That’s why the inverter is unable to power the pumping machine of 2.8kwa

  6. My name is Aaron. I use a submersible pump of 1.5 HP. This 2800wats. I have a Must PV1800 3kva inverter I have 8 100ah Solar batteries. Yet the entire system shuts down when I turn on the submersible pump. Inverter displays ⚠ 72 or ⚠4 which is translated as low battery or battery bus error.

    We’ve worked on the batteries by tightening all terminals. Yet problem still persist. And when the sun is so high and the pump stands on for about 10 seconds, the life wire from breaker to inverter gets hotter and begin to melt.

    Please help me fix

    • Your Inverter is undersized or your battery cannot provide the required amperage upon startup. 2800W is your running watts but your starting power is likely 2-7 times higher. This is where a high quality vs low quality inverter will show its true self. Since you have lots of batteries, my guess is that its an inverter issue.

    • Aaron, what gauge wires are you using to connect your inverter to the battery bank, and how long are they? The fact that they’re getting hot seems to imply that there’s too much resistance, so if the inverter can’t pull enough amperage, it will shut down (and the wires will get hot).

      Assuming your battery bank is 12V, running a 2800W pump would need to draw approximately (2800W / 12V) = 233 Amps from the batteries. This doesn’t take into account the current spike required to start up the motor. To handle that, you’d need at least 4/0 gauge wire (and at least a 250A breaker). The wires from the battery bank through the breaker to the inverter should be as short as possible – no more than a couple of feet.

      If your battery bank is 24V, you’d need at least 2/0 gauge wire (but 4/0 would be best).

    • 1.5hp is only about 1100W, but the pump probably requires about 50% more than that, so 1700W, not 2800W. The surge of your pump is massive. Surge currents can be 3-6X the run currents and last for seconds. Extremely difficult to run large electric motors off cheap high frequency inverters. I have a 3/4hp jet pump that hammered my 2kW/4kW high frequency inverter – would shut it down. My 4kW low frequency unit with 10kW/30seconds surge barely notices when it comes on.

    • You may want to check the quality and size of wire used for your connection. Probably double 16mm(32mm) flexible wire may do the job. Secondly reduce the distance between the inverter and battery as much as possible. Use good and thick cable lock to terminate the cable on the battery end. Then change your inverter to a 5KVA rating probably running on 48v system, then your sumo will power up efficiently without issues. Cheers

  7. Alan Mainwaring June 6, 2020 at 1:53 am Reply

    Hi there Borhan, I am in two minds about this , I have been using two MPP high frequency 4Kw solar inverters for now over three years and they have not missed a beat. They are in parallel and can deliver 8KW’s no problems.
    They cost about $1300 each Australian. I really love them make sure you don’t buy clones. We now have MPP Solar agent in Australia.
    I also have a Victron low frequency 5KW inverter as a last resort backup. Yes it is built like a Sherman tank, but boy it is heavy and expensive at $5000.
    Years ago I was involved in repairing High Frequency inverters, and i dreaded them, they where so unreliable and where very difficult to repair but times have changed, high frequency inverters are compact, light and much cheaper and also they have become much more reliable. I personally will stick to the High frequency Inverters , but make sure you buy from a reputable company, the Chinese clones do have issues in reliability. The company in Taiwan MPP Solar so far has given me a good service.
    As I said I am in two minds over this, its not that straight forward as some said ‘modern technology will bite you on the bum” what was true years ago is now no longer true. Yes i prefer High Frequency inverters because modern technology has solve any of the issues they had.

  8. We are considering using solar to power a cooler of approximate 2 refrigeration tons capacity. Usage of cooler is approximately 8-12 hours a day. Could you estimate the solar system that can be used for this purpose in terms of solar panel size, battery with controller and inverter. Then please do inform us the estimated cost of the system.

    Thank you

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