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Differences between Pure Sine Wave Inverter and Modified Wave Inverter

Aug 07, 2019

1. Invertion mode 

Pure-wave inverters usually use PWM, some even add multi-step invertion. Although the structure is more complex, the output waveform is quite good, suitable for inductive and capacitive loads. The modified-wave inverters are usually square-wave inverters, and only a few is added with step-invertion. The structure of the inverters is simple, and the output waveform is bad, so they are not suitable for inductive and capacitive loads.

2.Output filtering

Pure-wave inverters adopt multi-stage LC filters to obtain relatively pure sinusoidal waves. Modified wave inverters adopt single-stage LC filters, so the output approximates ladder waves.

3.Electromagnetic pollution

The output of sinusoidal RNZ power supply inverter is the same or even better sinusoidal AC as the power grid we use everyday, so it does not cause electromagnetic pollution in the power grid. Square-wave RONZ power supply inverters output square-wave AC with poor quality, and its positive maximum value almost occurs at the same time as its negative maximum value, thus causing severe unstable effects on the load and the RONZ power supply inverters themselves. At the same time, its load capacity is small, only 40-60% of the rated load, which can not carry inductive load. If the load is too large, the third harmonic component in the square wave current will increase the capacitive current flow into the load, and seriously damage the power filter capacitance of the load.


Pure sine wave inverters are applied to inductive loads (such as motors) while modified wave inverters are applied to resistive loads (such as incandescent bulbs). The principle of choosing between pure sine wave and modified wave inverters is based on the electrical characteristics of loads. The prices of the two inverters vary greatly. 

Some household appliances, such as bulb lighting, TV, computer, rice cooker, etc., can use either modified wave inverters or pure sine wave inverters. The impact made by modified wave is not very big. Modified wave inverters can be chosen when considering the cost. Ordinary air conditioning (Note: 1P air conditioning equals 735W, so we need to use modified wave inverters of 800W, but meantime note that sometimes 1P air conditioning may reach 1000W, so let’s estimate that it is 850W). The instantaneous starting power is 3-5 times the rated power for motor, refrigerator and other electrical appliances, for which we recommend using sine wave products  according to 3 times’ calculation ( eg. For an air conditioner of 2hp /1500W, we recommend 4500W, but our products of 4000W can also drive that air conditioner, because the peak value of our products is 6000-8000W, the peak value is equal to the maximum value of the instantaneous power of impact ). For the modified wave inverter to drive an appliance, we need to calculate with 5-7 times the rated power, but still it will damage the electrical appliances themselves. In general, we do not recommend customers to use modified wave inverter for frequency conversion air conditioning, induction cooker, which are also inductive loads, but they do not have instantaneous starting power value.

Generally speaking, sinusoidal RONZ power supply inverters can provide high-quality AC to drive any kind of load, but the technical requirements and costs are high. Some precision electronic devices and inductive load appliances must use sinusoidal RONZ power supply inverters. Otherwise, it may lead to abnormal operation of related electronic equipment, or even worse it may cause damage to equipment and RONZ power supply inverters or shorten the expected service life of equipment. Quasi-sinusoidal RONZ power supply inverters can meet most of our daily power needs, with high efficiency and low noise.