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Transformer harmonics

The harmonics are created by the loads that the transformer supplies power to. If your loads include a high percentage of electronic loads like IT equipment, electronic ballast lighting, electronic motor controls, etc., there can be a very high amount of harmonics that circulate back to the transformer. The harmonics create an increase in the neutral currents. Most standard transformers are not designed to handle the higher harmonics and corresponding high temperature. Type K rated transformers are designed withstand the higher harmonics, without derating the transformer or limiting its maximum load. There are harmonics filters on the market as well as the use of isolation transformers.

B/H curve of the magnetic material forming the transformer core is not linear, so if a sinusoidal voltage is being applied for a sinusoidal current (and hence sinusoidal flux & a sinusoidal secondary voltage), the magnetizing current is not sinusoidal. Thus the magnetizing current of a transformer having an applied sinusoidal voltage will comprise a fundamental component and various harmonics. The magnitude and composition of these harmonics will depend on the magnetizing characteristic of the core material and the value of the peak flux density.

By the way:
- The standard Transformer "Non-saturated" generate Harmonics only in transient case when the power is supplied, and after this too small time it doesn't generate any kind of Harmonics
- The Transformer generates Harmonics if it's saturated
- We should take care when selecting the Transformer's Power if there are a lot of installed Non-linear Loads, so for this case, we can select the power after define the correction factor by using the special curve done by "IEC", or calculating this factor by using a special Formula done by "UTE - France".

All AC signals are sinusoidal and periodic. These periodic signals can be resolved into a kind of trigonometric series - fourier series which is a summation of a fundamental and multiples of fundamental frequency.

The moment there is slight distortion from sinusoidal nature , it leads to harmonics in addition to the fundamental signal.. One way is to use DC signals... no harmonics.

As long as the AC signal is perfect sinusoidal , load & source is linear, there will be no harmonics. The way to get rid of harmonics is to have perfect source and perfect loads.

The non linearity introduced due to energy storing magnetic circuits, switching circuits, energy converting & inverting circuits distort the waveform to non sinusoidal. Therefore leads to harmonics. .

The way, there are antibiotic medicines for diseases. One needs to install the filter devices, which produce counter currents to suppress the effects of harmonics. The filters contain capacitors, inductors & power electronic components which are switched in anti-phase to harmonics producing elements. Thereby absorb harmonics.

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