How are harmonics produced and how they affect electrical system?

[bigjoe]

hi!

I am confused about harmonics, just want know how they are produce and how they affect the electrical system?
Are these harmonics are caused by the effects of electronic equipments and goes back to the electrical system?
Anyone knows where can I find a good discussion about harmonics?

thanks in advance!!

 

[Miguel Gaspar]

harmonics

Harmonics are n times the fundamental:
example: fundamental 60Hz
1st harmonique 120Hz
2nd harmonique 180Hz etc.

when you conect a device like TV, radio or a motor they generate harmonics while they are working for several factors like non linearity devices.

There are several standards to reduce this noise and several devices to reduce it, like common mode filters, chokes, magnetic beads.

If you are interested in more look up for THD.

 

[electronics_kumar]

harmonics

non linearity is reason for harmonics production....any /all nonlinear device will produce harmonics..
//
harmonics is nothing but multiplied version of fundamental frequency...

Added after 1 minutes:

In communication,FET BJT and diode are used generate harmonics...


hope my post helps

 

[jjohn]

harmonics

3rd Harmonics is detrimental

 

[maharshi_qis]

Re: harmonics

Harmonics are due to the nonlinearity in the various ckt components....

 

[rabel126]

Re: harmonics

suppose if u make the analsis of square wave of certain frequency u will came to know that it is made up of sine waves of different frequencies and amplitudes. the frequencies of all these sine waves are interrelated. the sine wave of lowest frequency is called fundamental frequency and other frequencis of sine waves are integral multiple of lowest frequency. the lowest frequency signal is called fandamental frequency and all other frequencis are called as its harmonics
The forier series of square wave is given below for any further information plz refer to engineering ciruit analysis by william j hayt

V(t)=sinwt+(1/3^2)sin(3wt)+(1/5^2)sin(5wt)+(1/7^2)sin(7wt)..........................

w is called fundamental frequency and 3w , 5w 7w and so on all r its harmonics

regarding abt the generation of harmonics take example of half wave rectifier with a pure inductive load a large number of harmonics are generated due to behavior of inductor and diode

 

[mostafa0020]

Re: harmonics

regarding their effects on power systems, harmonics affect the PS :-
1- higher losses " transformers, motors ,...etc"
2- parasitic torqus in motors,
3- telecomunications interferecne.
4- aging of equipment.
5- protective gear mal-functioning " nuissance tripping ".
6- voltage waveform distortion due to circulating harmonic currents through the system which has some impedance resulting in harmonic voltage drop which produces file voltage waveform distortion.
7- Zero-crossing operated circuits poor operation.
8- metering inaccuracies.
9-derating of Generators, Transformers., cables.
10- Resonance problem can arise resulting in very high currents and excessive overvoltages.
11- Neutral currents in three phase circuits, as the third harmonics add to each other in the neutral condutor, this can result to values of neutral current of 1.71 phase current.

 

[suvendu]

harmonics

harmonics means multiple of fundamental frequency.these are generated becoz of nonlinearity of the device...

 

[the_edge]

Re: harmonics

Search for Fourier analysis, you will find so much about harmonics....

 

[mma]

Re: harmonics

any signal we can represent it by a dc and cos and sin using Fourier series every term of the Fourier called harmonic there s 1st harmonic 3rd harmonic and so on

 

[si14]

Re: harmonics

huh?

 

[student153]

Re: harmonics

in AM range i.e .5MHz to 1.6 MHz there is interference between power line and telephone lines there is one thing in power line called corone effect which produces noise and power loss .corona occours when sinusoidal voltage of the line increses above such that it crossess the dielectric strength of air so current flows only when actually corona is occuring so it produces non sinusoidal waveform as you know every waveform can be represented in the form of sin functions(fourier) so harmonics are produced for further assistance see "b.l theraja"

 

[Yarafat]

Re: harmonics

hamonic such that if the frequency of the power system is 60HZ so its first harmonic or fundamental is 60 and its second is 2*60=120HZ, its third is 3*60=180HZ and so on. Especially, in power system, it always produce third harmonic in order to get sinusoial voltage at generator terminal.

 

[sonal]

harmonics

In acoustics and telecommunication, the harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency. For example, if the frequency is f, the harmonics have frequency 2f, 3f, 4f, etc. Harmonics come from the mathematical ability through fourier decomposition of any periodic signal into sine waves with frequencies integer multiples of the fundamental frequency.

Many driven oscillators, including the human voice, a bowed violin string, or a Cepheid variable star, naturally tend to be periodic, and thus can be decomposed into harmonics.

Most passive oscillators, such as a plucked guitar string or a struck drum head or struck bell, naturally oscillate at several frequencies known as overtones. When the oscillator is long and thin, such as a guitar string, a trumpet, or a chime, the overtones are integer multiples of the fundamental frequency. Hence, these devices can mimic the sound of singing and are often incorporated into music. Overtones whose frequency is not an integer multiple of the fundamental are called inharmonic and are often perceived as unpleasant.

The untrained human ear typically does not perceive harmonics as separate notes. Instead, they are perceived as the timbre of the tone. In a musical context, overtones which are not exactly integer multiples of the fundamental are known as inharmonics. Inharmonics which are not close to harmonics are known as partials. Bells have more clearly perceptible partials than most instruments. Antique singing bowls are well known for their unique quality of producing multiple harmonic overtones or multiphonics.

The tight relation between overtones and harmonics in music, often leads to their being used synonymously in a strictly musical context, but they are counted differently leading to some possible confusion. This chart demonstrates how they are counted:

1f 440 Hz fundamental frequency first harmonic
2f 880 Hz first overtone second harmonic
3f 1320 Hz second overtone third harmonic
4f 1760 Hz third overtone fourth harmonic