Excel Electrical Infra

Excel Electrical Infra

AC Harmonics #4



In an electrical system, a component of the current or voltage which does not consist of the fundamental frequency is harmonic. Source of harmonic content in the systems are power electronic equipment, non-linear load, surge, saturated magnetic material, and inrush currents.





In general, any nonsinusoidal can be expressed as a Fourier series :



Fourier series in equation (1) can express as follow



where, 



Using equation (2), RMS voltage is :



Here, $V_{1rms}$ component is with the fundamental frequency. So, only $V_{1rms}$ is desirable and other components are considered as harmonics.


In equation(8) $V_{oh}$ is the RMS value of harmonic content in the waveform. Dividing equation (8) with respect to the RMS value of the fundamental component will give total harmonic distortion (THD).




where g is the distortion factor 






Displacement factor (DF) (Fundamental power factor)



Where, $\theta_1$ is angle between $V_{1rms}$ and $I_{1rms}$

Post a Comment

0 Comments