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Concept of Harmonics...

  1. Mar 30, 2016 #1
    Hi, please help me with the following questions !
    can we say that harmonics are because of Reactive Power (i know that one way of controlling harmonics is filtering) ? IF YES, can we control Reactive power by increasing Power Factor ? IF YES it means Harmonics can be controlled by increasing Power Factor ? Does Harmonics occurs by supplying a pure DC current to non linear load ?
     
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  3. Mar 30, 2016 #2

    anorlunda

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  4. Mar 30, 2016 #3

    jim hardy

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    anorlunda is right.

    Harmonics in electrical power discussion come about when something departs from a sine wave.
    Read up on Fourier Analysis
    any continuous repetitive waveform can be expressed as a sum of sinewaves of different frequencies
    that of the basic wave that's repeating itself
    plus all its harmonics, each multiplied by a proportioning coefficient and shifted in phase

    The electric company goes to a lot of trouble to keep the sinewave pure
    but harmonics creep in.

    Start with this wiki article
    https://en.wikipedia.org/wiki/Harmonic_analysis
    two images from it:
    here's the waveform of a bass guitar string making a 55 hz A note
    400px-Bass_Guitar_Time_Signal_of_open_string_A_note_%2855_Hz%29.png

    and a plot of its Fourier Analysis
    400px-Fourier_Transform_of_bass_guitar_time_signal.png
    each peak is a harmonic, observe 55hz(first) 110hz(second, and as expected pretty small) 165(third) 220(fourtg) and so on.

    That's the simplest concept of harmonics. Deviation from a sinewave and "Dr Fourier's Painless Transform"..

    There are small portable instruments that display the Fourier Analysis of a signal. They are really handy for maintaining rotating machinery because the harmonic content of a vibration signal tells you a lot about what's going on in the machine.

    I hope that helps with the concept.
     
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