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Thread: Electrical harmonics

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    Bronze Member mikilianis's Avatar
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    Electrical harmonics

    Hi I have a question it might be a bit on the wild side but here goes, What is harmonics can anyone answer that one in laymans lingo

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    Platinum Member Marq's Avatar
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    OK - I'll have a go at trying simple:-

    Sound is defined as a wavelength.
    The wavelength will have a certain frequency. (higher frequency hight pitch sound)
    To us it sounds like one wavelength and one frequency....but in fact
    It is made up of multiple frequencies
    Its like you get the main sound frequency and then multiples of that frequency higher and lower.
    Those multiples are called the harmonics.

    So say you get a frequency sound at 440Hz - the main sound you will hear.
    There is also a sound at the same time at 880Hz...1320Hz...1760Hz etc.
    These are the harmonics also called the overtones.

    If you listen to an overtone singer like Michael Vetter for eg. you will hear him 'hum' or sound the basic notes and then you can also hear at the same time other higher pitched notes that result from the lower note. They are harmonious notes that result from projecting the original wavelength - the higher pitched note is the harmonic of the lower pitched note.

    If you listen to a Tuvan Undertone singer - it sounds strange and child like and one laughs them off - but these guys sing/sound the basic notes and then create an overtone and an undertone at the same time. When you see what they are doing it is actually amazing stuff which gives one a new insight into their world.
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    harmonics are problems in an electrical system caused by non linear loads and non sinusoidal waveforms.

    they heat neutrals
    damage transformers windings...etc

    zero sequence harmonic currents also commonly called triplen harmonics cause lots of problems.

    harmonics can be reduce with the use of correct filters.

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    Platinum Member Marq's Avatar
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    I thought the question was electrically alligned but did not know how. So do these harmonics in electrical currents relate to the same wave forms found in sound? ie say 50hz in electrical system generating a 100hz and a 150hz sub current which is creating the problems you are referring to?

    I know as much about electrics as an mp knows about a work day so if its huge and complicated just give me the short version like go away......
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    Site Caretaker Dave A's Avatar
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    By my understanding, to some extent you're on the right track, Marq. Having multiple wave patterns can get pretty exciting when one wave pattern is somehow in harmony with another. You can end up with higher voltage spikes, unexpected current flow, or phasing as the different wave forms fall in and out of sync.

    This results in the sorts of problems Murdock referred to.
    Last edited by Dave A; 16-Aug-09 at 09:04 AM.
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    A easy way to understand is that the Sine Wave in AC current is repeated more than the 50 times e.g. 3rd harmonic is 3 x 50 hz. Because of this one experience a lot of heat on 3, 5, & 7 harmonic. OR call it colesterol of your conductor. It makes it difficult for the "normal" current to flow. Hope it help. I have a full Power Point presentation on it if you need it.

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