Modified Sine Wave or Pure Sine Wave inverter – what is the difference?
There are 2 types of inverters on the market: “True” Pure Sine Wave and “Square” Modified Sine Wave
Modified sine wave inverters
The output of a modified sine wave inverter is similar to a square wave output except that the output goes to zero volts for a time before switching positive or negative. It is the easiest way to convert DC to AC, all you need to do is to switch the output of the DC source (for example battery) back and forth, or in other words swapping the “negative” and “positive” leads, periodically, this produces a square wave. Special filters applied to this output to round the corners of the square wave, to call it “modified” but it still stays quite “square”.
This type of “modified” output is compatible with most electronic devices, but you should be careful connecting sensitive or specialized equipment like computers, fluorescent lights and audio equipment as this type of equipment was not originally designed by manufacturer to be powered from “Square” wave AC power, because it will almost certainly cause them to overheat. The reason for this is that modified sine wave power inverters have a combination of too much noise and harmonic distortion compared to a pure sine wave inverter or mains AC grid power. If you use a square wave the amount of power the load has to deal with goes up, and extra power means extra heat, and the difference between a pure sine wave and a modified is actually quite noticeable and could easily be 20%-30% depending on the type of filter used in the inverter. Modified sine wave is can be used for “tough” electric devices like shunt or induction motors, some “switching” computer power supplies etc. Some electronic equipment can deal with it pretty easily and the others not so well simply because they were not designed to handle anything but “clean” AC. In the end you can only go by what the manufacturer says if you want to be sure.
Pure Sine Wave Inverters:
The output of a modified sine wave inverter is perfect sine wave (ideally, but in reality depends on manufacturer) output that is exactly the same as supplied grid AC power. To produce pure AC is much more difficult because it takes more components, but this type of power output makes it compatible with almost all AC electric devices you usually use in your house. This type of inverters are designed to operate sensitive electronic devices that require high quality and stability characteristics of AC waveform with very little harmonic distortions, and that makes them suitable for most electronic devices designed to be powered from AC power. I think we can safely say that any electronic device you may have in your house will operate with the output from a pure sine wave inverter. Most quality inverters have 40%-100% surge capacity which means they are able to exceed their nominal rated wattage for a short period of time, usually 5-15 seconds, which is enough to start a motor or a fridge without the risk of destroying your valuable inverter in first seconds of high start-up power surge.