What is low frequency inverter? Why choose it?
For those who want to build off-grid systems or backup power systems, including solar inverter systems, inverters are one of the most important parts. Inverters convert DC power (DC, 12V, 24V or 48V) stored in batteries to AC power (AC, 120V/240V) that can be used to run your household items and appliances, from refrigerators to TVs to cell phone chargers. Inverters are a must-have item for those who do not have access to mains power, as they can easily provide a large amount of power.
There are two types of power inverters on the market: low-frequency inverters and high-frequency inverters. Whether the inverter is high-frequency or low-frequency, each design has its advantages and disadvantages.
What are the advantages of low frequency inverter?
Low-frequency inverter has the advantage of simple structure and various protection functions can be realized at lower voltage. The inverter is stable and reliable, with high overload capacity and shock resistance, and can suppress the high harmonic components in the waveform because of the presence of a frequency transformer between the inverter power supply and the load. However, the IFT transformer is also bulky and expensive, and its efficiency is relatively low. Small low-frequency inverters made at the current level generally have a rated load efficiency of no more than 90%. At the same time, because the iron loss of IFT transformers is basically unchanged when operating under full load and light load, thus making its no-load loss larger and less efficient when operating under light load.
Two Areas: Peak Power Capacity & Reliability
Low-frequency inverters have advantages over high-frequency inverters in two areas: peak power capacity and reliability. Low-frequency inverters are designed to handle higher power peaks for longer periods of time than high-frequency inverters.
1. Peak Power Capacity
According to the spectrum distinction table prepared by the Institute of Electrical and Electronics Engineers (IEEE), the low frequency is 30~300kHz, the middle frequency is 300~3000kHz, and the high frequency is 3~30MHz. The frequency plan in 30~300MHz is VHF, and in 300~1000MHz is UHF. Compared to the low frequency signal, the high frequency signal changes very fast and has sudden changes; the low frequency signal changes slowly and the waveform is smooth.
In fact, low-frequency inverters can operate at peak power levels for several seconds. This power level is up to 300% of its rated power level, while the high-frequency inverter can operate at 200% power level for a fraction of the time.
The second main difference is reliability: low-frequency inverters operate with powerful transformers that are more reliable and robust than the MOSFETs of high-frequency inverters. The latter use electronic switches that are more prone to damage, especially at high power levels.
In addition to these qualities, the low-frequency inverter has a variety of technical features and functions that are lacking in most high-frequency inverters. These features and functions include a built-in battery charger, UPS (Uninterruptible Power Supply) function, bypass mode without battery connection, power saving mode and various charging settings (such as different battery types and charging voltages).
In terms of these differences, low-frequency inverters are designed for large off-grid power systems and are better suited to be equipped with powerful appliances. Therefore, they usually belong to the high power category of solar charge inverters.
Should you choose a low frequency inverter?
Low frequency inverters are not for everyone. They are very large and much heavier than high frequency inverters. Best suited for those who are building an off-grid power system with no significant power limitations. Or those running high power appliances and equipment with motors such as power tools, washing machines, vacuum cleaners and air conditioners. Low-frequency inverters are also best suited for those who want to power a variety of kitchen appliances such as refrigerators, microwaves, dishwashers, and ovens.
The increased peak performance capability and reliability of low frequency inverters means that they cost more than high frequency inverters. If your energy consumption is small and only small appliances need to be powered, or if you have limited space to place the inverter, then a high frequency inverter would be better for you.
Low-frequency inverters remain an excellent investment for those with a large number of high-power appliances in locations where standard power is limited or unavailable. Coupled with the right off grid solar kit, low-frequency inverters can not only provide a reliable backup power solution, but they can completely replace conventional power with power of the same quality. Given that low-frequency inverters are less likely to fail, the price you pay for a low-frequency inverter is higher than a high-frequency inverter and should be considered a long-term investment. They are indeed bigger, stronger and more robust.