Passive Harmonic Filters are currently the most common method used to control the flow of harmonic currents. They are built using a series of capacitors (capacitance) and reactors (inductance) forming an LC circuit in parallel with the power source. Generally Passive Harmonic Filter provide the low impedance path to Harmonic current and that way eliminate the Harmonic current in system.
Harmonics are an important aspect when considering power factor correction. The range includes a number of options to overcome these harmonics. Modern electrical equipment consists of nonlinear devices which generate harmonics.
Examples of these devices include the following: – Arc furnaces – In certain cases, transformers, reactors and rotating machines – Domestic appliances Harmonics are not only found in industrial networks, they can also spread into the distribution network and cause problems for other power users. Common problems that harmonics can produce include: – Overloading of capacitors, leading to malfunctioning and premature aging – Increased losses, e.g.Machines will operate at increased temperatures – Resonance problems between the inductive and capacitive parts of the network – Malfunctioning of control systems – Interference with telecommunication and computer equipment – Electronic Card Failure – Disturbances in ripple control systems – High currents in neutral conductors Harmonics distort the sine wave (50 Hz or 60 Hz) sign which becomes apparent when a distorted sine wave mathematically analysed. – Equipment containing electronics that control other apparatus. E.g. variable speed drives
