Power Inverter Selection Guide 2021

Power Inverter Selection Guide 2021

How to choose power inverter correctly is the question of every user cares about. There are many different inverter on the market, and their prices, sizes and weights are very different. How to choose an inverter that suits you, it is a difficult problem for many users. This article Power Inverter Selection Grid will provide you with answer to the differences between various power inverters from different perspectives of work reasons and output waveforms. It will also bring you the answer that how to choose correct power inverter and configure your inverter system in different usage scenarios and loads. For example, how will the off-grid solar system you need to be matched with inverters, batteries and solar panels, what type of combination of inverters and batteries is more suitable for solar system on RVs, and on professional vehicles (Refrigerated vehicles, Ambulances, Rescue vehicles, Communication emergency vehicles) how to correctly configure the power system. 



From the working principle, it is divided into low frequency inverter and high frequency power inverter:

Low frequency inverter: firstly, the DC power is inverted into low-voltage AC power at low frequency, and then boosted by a low frequency transformer into 120VAC or 220VAC, 50HZ or 60HZ AC power for the load.

The advantages of the low frequency inverter: simple structure, because there is a low frequency transformer between the inverter module and the load, the inverter is stable and reliable, with strong overload capacity, and the peak power can reach 3 times.

The disadvantages of the low frequency inverter: because of the low frequency transformer, its weight is very heavy, generally more than 5 times of high frequency inverter. Its efficiency is also very low, usually the conversion efficiency of a low frequency inverter is only between 60%-70%. The self-loss is very large. If your battery is not large enough, it will be quickly consumed when the inverter has no load. General low frequency inverter, according to the current technology, its power factor can only reach 0.8. This is why many low frequency inverters are marked as kva. 1000kva low frequency inverter with power factor 0.8, its largest output is only 800W.

The high frequency inverter first uses the high frequency DC to DC conversion technology to invert the low-voltage DC into high-frequency and low-voltage AC, than boost the voltage through the high frequency inverter, and then rectify it to 300V-400V through the rectifier filter circuit high-voltage DC, and finally through the inverter circuit to get 120VACor 230VAC, 50HZ or 60HZ AC for the load to use.

The advantages of high frequency inverter: Because the high frequency inverter uses a small and light-weight high-frequency magnetic core material, the power density of the circuit is increased. And the volume of high frequency transformer is smaller than that of the low frequency inverter., so it has the characteristics of light weight and high efficiency. Its conversion efficiency can reach more than 94% at 48VDC, the quiescent current of 120VAC or 230VAC 1000W is only 9.6W, which is very suitable for use in vehicles anf solar systems.

The disadvantages of high frequency inverter: because the circuit design of high frequency technology is used between the inverter module and the load, the peak power is only twice the rated power, so its impact resistance is worse than that of low frequency inverters. At present, CNBOU's BPlus series pure sine wave inverter has overcome this problem, and it is the only high frequency inverter with 3 time peak power on the market.

Divided by output waveform: Modified sine wave inverter and pure sine wave inverter

The modified sine wave inverter is optimized on the basis of the square wave inverter. Compared with the suqare wave inverter, the output voltage  waveform is significantly improved, and the harmonic content is also much smaller than that of the square wave inverter. The modified sine wave inverter adds a delay in the time period when the voltage is 0. Because this delay is added, the battery will not change suddenly, from +220V to -220V to +220V to 0V to -220V. This change makes the modified sine wave inverter suitable for ordinary resistive loads, but it is still not suitable for capacitive loads and inductive loads. If you use inductive loads to have a certain impact on the electrical load, the load will burn out in severe cases.

The advantages of modified sine wave inverter: low price, very cost-effective for users with only resistive loads.

The disadvantage of modified sine wave inverter: large harmonic interference, poor carrying capacity, not suitable for capacitive and inductive loads.

The pure sine wave inverter simulates the voltage change of the mains power through a complex circuit, and its output power quality is the same as or even better than that of the mains. The output waveform is highly cosistent with the waveform of the mains. Because the mains power is used for very complex loads, there will still be a certain amount of harmonic interference. The pure sine wave runs independently, normally the pure sine wave provides higher AC power than mains. It is suitable for running all types of loads, including resistive loads, capacitive loads and inductive loads. Good quality pure sine wave inverters are more suitable for radios, communication equipment, medical equipment and precision instruments.

The advantages of pure sine wave inverter: suitable for all types of loads, with high stability and low harmonic interference.

The disadvantages of the pure sine wave inverter: Compared with modified sine wave inverter, the price is higher.

Resistive load:

There is no phase difference between the load current and the load voltage of resistive load. The internal load is resistive, such as incandescent lamps, electric furnaces, etc. The load that only produces effects through electrical components is a resistive load. This type of load has low requirements for voltage and waveform, similar to incandescent lamps, when the voltage is low, the brightness will follow to dim, but it will not affect the incandescent lamp.

Capacitive load:

Capacitive load refers to the existence of a capacitor in the load. Because of the characteristics of the capacitor, it needs a very large current instantaneously. Due to the phase difference, the current of the load exceeds the voltage of the load, thereby reducing the power factor of the circuit. We call capacitor or other similar components with capacitive parameters inside as capacitive load. The starting power of this type of load is usually 2-4 times the rated power. For example, a fluorescent lamp with a rectifier has a rated power of 8W, but the actual starting power will between 15W-40W, this is a relatively common capacitive load. There is a speical capacitive load, which is the charger of  various devices, especially the battery charger. If the quality of the charger is not good enough, it will produce a large haemonics, which will interfere with the inverter. In our actual test, an 2000W pure sine wave inverter with a 1000W battery charger has very large interference, and even cannot start normally. There is also an electric blanket, because the layout of the resistence wire for heating is looped, it will also cause very big interference. A normal 100W electric blanket and a 600W pure sine wave inverter will not work properly.

Inductive load:

Inductive load refers to the load with inductive parameters in the load, which are made using the principle electromagnetic induction. Since the current change caused by the phase difference with the power supply lags behind the voltage, a larger current is required at startup. The instantaneous power of a general inductive load is 4-7 times the rated power, such as motors, compressors, electric fans, air conditioners, washing machines, etc. If you use this type of devices, please use the pure sine wave inverter that is 4 times higher than the rated power, because the peak power of the pure sine wave inverter is 2 times the rated power, which has actually reached the inductive load 8 times the peak power at startup. Of course, this kind of load has very high requirements on the waveform, and the modified sine wave inverter is not suitable for this kind of equipment. If used for a long time, the equipments will be damaged and cannot be repaired.

According to the load situation, choosing the right power inverter will save you a lot of unnecessary trouble.

We found the many users are confused about how to choose home inverters and batteries. This article will list some of the equipments used in the home, which can help you to choose the correct combination of inverter and battery according to the different equipments and frequency of use. In this table, we use a standard brand new lithium iron phosphate battery and pure sine wave inverter, because lead-acid batteries have different characteristics, the calculation method is not standard,  we will use a brand new 1C lithium iron phosphate battery.

Our calculation method is basically based on the type of load, judging wether it is a resistive load, a capacitive load or an inductive load and calculating its starting power (surge power) according to the load type to match the inverter. We will have 10%-20% margin to calculate the required inverter power. The continuous working time is calculated based on 80% of the battery capacity, considering the conversion efficiency of the inverter and the remaining 5% of the battery capacity. Although our calculations are very detailed, there are still differences between different loads, batteries, inverters. Please choose as much margin as possible.

CNBOU has ten years of power inverter manufacturing experience and hundreds of thousands of customer user scenarios. We share our solution and professional advice, we believe it can help you to choose the correct power inverter.


Author: Rico Chen by CNBOU


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