can any one give me the idea about the harmonics in the ac supply?

Question

details abt the harmonic orders......

Answer 1

Conducting a fourier analysis on the generated waveform you can get the harmonics,order of the harmonics and the percentage of the harmonics present in the AC waveform.

The major harmonics present on an AC waveform are the 3rd and 5th harmonics with minor presence of 7th harmonics.

Now what is a 3rd harmonics or 5th or7th harmonics?

Supposedly the system has an operating frequency of 50Hz.That means the 3rd harmonic will have a frequency of 150 Hz and the 5th Harmonic will have a frequency of 250Hz and 7th will have a frequency of 350Hz.

These high frequency waveforms cause high heating in the windings of the transformers and other electrical equipments connected to the system.Hence suitable measures are to be taken in order to reduce the higher harmonic contents in any AC waveform.


Higher harmonics are typically found in chopper circuits using diodes.The outgoing AC waveform is filtered through LC supression circuits to reduce the higher harmonic content.

Ossillograms are typically used to view the waveform and the harmonic contents in the output waveform of chopper circuits.

Answer 2

If you are referring the the harmonics coming out of the wall outlet from your mains, they are mostly odd harmonics of the local frequency (60 or 50 cycles) and are due to the fact that transformers are non-linear. Put in a sine wave, get out something with harmonics.

Answer 3

What causes harmonics that bother computers. All power supplies have diodes that turn on and off to let the current flow one direction . The capacitors are charged and so the voltage doesn't drop to zero when it actually turns off. The results of this there will only be current flow about 30% of each half cycle. In the neutral this will cause square waves depending on the phases etc. If your safety ground and neutral is connected any place except the transformer it will cause current flow in the safety ground. This makes the computer signals riding in a mess of sq. wave noise.

Answer 4

harmonics are the results of a faulty circuit, flaws in the design makes electronic frequency dynamics within the analyzed spectrum cancel and multiply and creates a problem called harmonics, most engineers see this problem as a natural order, and measure it with a practical formula, but by experience i ve designed circuits with unmeasurable harmonics, and these circuit principles will occupy the production industry in the very near future, and harmonics will be in the history books.

Answer 5

to properly calculate signal harmonics, you must conduct Fourier analysis on your waveform. You may for example, end up with odd harmonics, for example 3rd, 5th, 7th etc harmonics.

Answer 6

Check this out:

http://us.fluke.com/usen/products/Fluke+345.htm?catalog_name=FlukeUnitedStates&Category=PQTTOP(FlukeProducts)
http://ecmweb.com/powerquality/electric_harmonics_made_simple/
http://ecmweb.com/powerquality/electric_harmonics_made_simple/