Modified Sine Wave Inverter

March 17th, 2017


automotive accessories


Modified sine wave is the main waveform of inverters in today’s market. Modified sine wave inverter belongs to the square wave inverters but have optimized performances in some facts. Compared to pure sine wave inverters, modified sine wave inverters have many advantages and limitations at the same time. Knowing more about modified sine wave can help you use inverters safely and correctly.

Why is modified sine wave needed?

Pure sine wave inverters apply isolation coupling circuit. The AC current a true sine wave inverter provided is much smoother and more stable. While square sine wave inverters bring AC current in the form of square wave so that the maximum and minimum current arrive almost at the same time, which may bring great hidden instability to load and inverter itself. At the same time, the inverter’s load may be 40%~ 60% of rated load that can’t support inductive load. If there’s too much load, the inside third harmonic will increase the capacity current and damage the filter capacitor.

According to the disadvantage of square sine wave inverters, modified sine wave inverters come into being accordingly. There is a pause in the output wave of modified sine wave inverter between the positive maximum current and the negative maximum current so as to bring a better using experience than that of square inverters. While the waveform of modified sin wave inverters still consists of broken lines, so modified sine wave is still kind of square wave inverters. Compared with pure sine wave inverters, modified inverters are more inexperience and more practical in common use. But when it is used for running precise equipment, there may be high frequency interference to communication equipment.

Modified sine waveform  

The diagram above is the waveform of pure sine wave and modified sine wave. The modified sine wave is trying to come close to the pure sine wave. Compared with pure sine waveform, the modified waveform is more winding with more pauses. There are more steps for a modified sine wave to flow from the positive max current to the negative max current. It still has a zero volt while the pause time is longer. The difference between pure sine wave and modified sine wave is more obvious when it comes to the current signal. The current signal of a modified inverter is discontinuous with tiny pauses while the pure sine wave inverters keep deliver a smooth and stale current signal.

Applications of a modified sine wave inverter

Though modified inverters are more widely used in common life than pure sine wave inverters, modified sine wave inverters have their limitations of using.

modified sine wave inverter can work well for ordinary equipment and appliances, like tablets, televisions, and cameras and so on, but may not operate well when used for precise equipment that may have delicate electronics or audio devices which need choppy waves. Some simple devices like old TVs and motors can function well with a modified sine wave inverter. Some appliances or motors may work fine buy may be hooter when running for a while. Because the total harmonic distortion of a modified sine wave is respectively higher and will cause up to 305 energy consumption. That may also reduce the life of your appliances. To better use the modified sine wave inverters, here are some application limitations of a modified sine wave inverter as follows:
1.    Devices with thyristor (an electronics component) like laser printers, photocopiers, vacuum cleaner, etc.
2.    Devices used in some washing machine controls, as they may have a silicon-controlled rectifier.
3.    Appliances that has speed/microprocessor controls like some sewing machines.
4.    Medical equipment like oxygen concentrators.
5.    Digital clocks with radios.
6.    Some battery chargers for cordless tools.
7.    Some fluorescent lights with electronic ballasts.
8.    X-10 home automation systems.

For most people, a modified sine wave inverter is a cost-effective electronic device to charge up common appliances or equipment. Take heed the above explanation of modified sine wave and waveform to wiser use modified sine wave inverters in real life.

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