21-09-2008, 10:01 AM
Today, the situation on low-voltage AC systems has become a serious concern.The quality of electrical power in commercial and industrial installations is undeniably decreasing.
In addition to external disturbances, such as outages, sags and spikes due to switching and atmospheric phenomena, there are inherent, internal causes specific to each site and resulting from the combined use of linear and non-linear loads.
Untimely tripping of protection devices, harmonic overloads, high levels of voltage and current distortion, temperature rise in conductors and generators all contribute to reducing the quality and the reliability of a low-voltage AC system.
The loads which consume non-sinusoidal currents are called as non-linear load.This type of load is used for the conversion, variation and regulation of electrical power in commercial, industrial and residential installations.
Acurrate signal conditioning plays an important role in voltage signals.Proper signal conditioning converts the high power signals to meet the requirements of the low voltage control circuits.Increase in non-linearity causes different undesirable features like low power factor and low efficiency.
Active harmonic conditioners are proving to be viable option for controlling harmonic distortion levels in many applications.It has been proved to be effective when the load is non-linear.
The effective operation of the active harmonic conditioner is based on the accurate sensing of the source current,source voltage and DC side capacitor voltage of the filter...