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[SOLVED] Importance of 3rd Harmonics

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tahir4awan

tahir4awan

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Importance of 3rd Harmonic

I was told that harmonics are due to non linear effect of devices.
What I think harmonics are unwanted signals(noises).
But I often read about 3rd harmonics so my question is what is the importance of 3rd harmonics and why?
If harmonics are noises then why don't we simply reject them why do we consider them in terms of order i.e 1st, 2nd, 3rd harmonics etc.
 
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Harmonics are only unwanted in linear circuits, there are many applications that deliberately create and use harmonics. They are particularly useful if you want to multiply frequencies, for example if you wanted frequencies of 2MHz, 3MHz, 4MHz and 5MHz, you could use four oscillators or just a 1MHz oscillator with harmonics and filter out all but the multiple you wanted. It's a technique used widely in radio receivers where 1MHz harmonics are sometimes used up to 50MHz or more.

Brian.
 
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)

+++
 
Guys thanks for helping me on Harmonics but I still ask what is the importance of 3rd harmonic?
 

It is the lowest of the "triplen" harmonics (3rd, 9th, 15th, etc.) which constructively interfere with the fundamental frequency to create distortion including an increase in peak voltage that is easier to measure than other harmonics.
 

OK last question the what is fundamental harmonic? is it the source signal itself or it is the first level harmonic?
 

Yes, Fundamental harmonic is the source signal. Fundamental frequency is also called as first harmonic.
 
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