tahir,
In Power electronic :
if you want assemble certain types of sinusoidal wave inverter, it is possible to filter higher harmonic components.
Due square have is formed by sum of all odd components ( 1st, 3rd, 5fth, 7fth, ... ), some inverters and UPS are made by filtering a finite amount of first even components ( 2nd, 4th, 6fth, 8fth, ... ). The result is a wave that seems like sinusoidal. It is not the best way to perform it. The only advantage is use of half of comutation components (MOSFETs)
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