Harmonics are the deviation or the distortion of the waveform of its Sinusoidal waveform due to the addition of waveforms of different frequencies.
As per Ohms Law V=I/R,Voltage is proportional to the Current means Current also have a sine waveform except current(which has power factor) does not align perfectly to voltage waveform.
As per Ohms Law V=I/R,Voltage is proportional to the Current means Current also have a sine waveform except current(which has power factor) does not align perfectly to voltage waveform.
Figure 2 shows the superimposition of the 3rd order harmonic to the base sine wave due to that the resultant waveform is Distorted waveform(Base+3rd Harmonic).The entire waveform does not follow the Sinusoidal pattern causes unbalance in the load.
The below Fig shows the distorted waveform which is the resultant of the addition of the 3rd harmonic with the fundamental pure sinewave.
The Equation of a Sinewave is written as:
V=VmaxSine(wt)
Note: The harmonics depend on Phase angle,Frequency and also the amplitude.
If the fundamental frequency is given as; E = Vmax(2πƒt),then the complex waveforms will be,The harmonics are voltages or currents that operate at a frequency that is an integer multiple of the Fundamental Frequency.
Name

Fund.

2nd

3rd

4th

5th

6th

7th

8th

9th

Frequency, Hz

50Hz/60Hz

100/120

150/180

200/240

250/300

300/360

350/420

400/480

450/540

Sequence

+

–

0

+

–

0

+

–

0

Note that in some countries the fundamental frequency will be either 50Hz(UK) or 60Hz(US).
Sequence

Rotation

Harmonic Effect

+

Forward

Excessive Heating Effect

–

Reverse

Motor Torque Problems

0

None

Adds Voltages and/or Currents in Neutral Wire causing Heating

Common Problems Caused by Harmonics
Overloading Neutral Conductors
The 3phase system consists of three phase conductors and a neutral conductor. These three phase conductors carry the same amount of current and they used to cancel each other in the neutral conductor makes the load balanced But due to the usage of motors,fans,rectifiers,SMPS causes neutral with increased or twice the current flow of phase current.Hence with balanced load with the currents cancel each other in the neutral conductor, the size of the conductor is minimum, but due to the nonlinear loads, the current draw is higher hence the size of the neutral conductor is bigger than the counterpart.
Overheating Transformers & Losses
Overheating Transformers & Losses
The Transformers feeding power to the unbalanced loads like rectifiers,motors, the eddy current loss in the windings is proportional to the square of harmonic current and its frequency thus the losses associated with the transformer with the nonlinear load will be twice of the linear load.This condition leads to the overheating of the Transformer which degrades the insulation causes complete failure.
Nuisance Tripping of Circuit Breakers
The RCCB used to check the current between phase to neutral if the neutral current is not same with the phase current then RCCB disconnects power to the Load and also RCCB does not sum the higher frequency components thus sometimes it used to trip.
Nuisance Tripping of Circuit Breakers
The RCCB used to check the current between phase to neutral if the neutral current is not same with the phase current then RCCB disconnects power to the Load and also RCCB does not sum the higher frequency components thus sometimes it used to trip.