Harmonic frequencies

Question 1

What are harmonic frequencies

Answer 1

Frequencies created by non linear electrical loads that are integer multiples of the source frequency (50HZ)

Question 2

What is a resultant waveform?

Answer 2

It is the result of sine waves of difference frequencies imposed on top of each other.

Question 3

What is the consequences of harmonic frequencies?

Answer 3

Wasted power and shortened life of equipment, increased heating of equipment and transformers. Reduced motor speed.

Question 4

What type of equipment creates harmonics?

Answer 4

All non linear loads. Electronics, LED transformers, VSDs, transformers.

Question 5

Up to what frequency are harmonics problematic

Answer 5

Utilities usually only measure harmonics up to 13th since above this they make such a small distortion to the waveform to be of little harm.

Question 6

What is outer skimming?

Answer 6

In higher AC frequencies the current primarily moves through the outer edges of the conductor. This reduces the effective cross sectional area of the conductor. This is primarily a problem with solid conductors such as busbars. Since harmonics increase the frequency then they can increase this problem.

Question 7

What strategies are used to deal with harmonics

Answer 7

Finely stranded conductors to reduce outer skimming effect. Larger neutral conductors. Filtering the harmonics using an inductor in series with a capacitor.