What are the causes of harmonics and the problems happen in industrial usage voltage.?

Question

my name is akapane kuroudo..now studying in japan in electronic control system engineering...sometimes, i have problems in my study such as difficulty to understand during classes..i really hope you can help me asnwering my question..

Answer 1

Harmonics are due to natural resonances is a system. If the system is stimulated in some way like with a pulse of electrical current it will briefly oscillate at some fundamental frequency and harmonics of that frequency. To avoid harmonics filters or devices to absorb them or change the natural frequent of the system must be installed.

Answer 2

An even worse problem occurs on airliners. Large numbers of in flight entertainment devices and VCRs use rectifier type power supplies. This can generate so much harmonic distortion that the aircraft alternator cuts out, causing a complete on board electrical failure. The answer is to use different types of power supplies in the entertainment system, that do not generate so much harmonic distortion.

Answer 3

Non-linear loads draw harmonic currents. Any load that includes a rectifier is non-linear. Examples of large non-linear loads include variable speed drives and DC welders. Small electronic devices such as computers also contain rectifiers and large numbers of them add up to a significant harmonic current.

Harmonic currents flowing in the power distribution system wiring, transformers etc. cause a voltage drop that results in harmonic distortion of the supply voltage.

One problem caused by harmonic current is similar to the problem caused by low power factor. If part of the distribution capacity is used to supply harmonic current, less capacity remains available to supply useful power.

Another potential problem is that harmonic voltages can cause resonance in supply system and load components leading to excess heating and other malfunctions. Even increased current in some loads without resonance can cause overheating.