Harmonic filters isolate harmonic current to protect electrical equipment from damage due to harmonic voltage distortion. They can also be used to improve power factor. The detrimental effects of harmonic distortion can be manifested in many different ways, such as increased heating effect on electrical distribution equipment and cables, electronics miss-timings (computers, fax machines, etc.), capacitor overloads, fluorescent light flickering, and others.
Important general specifications to consider when searching for harmonic filters include the type and the signal type. Filter types include passive or active. Passive harmonic filters are built with a series of passive components such as resistors, inductors and capacitors. Passive filters are most common and available for all voltage levels. They are built-up by combinations of capacitors, inductors (reactors) and resistors. Active filters are available mainly for low voltage networks. Active harmonic filters are very fast electronic devices that will insert negative harmonics into the network, thus eliminating the undesirable harmonics on the network. The filters are built with active components such as IGBT-transistors and can eliminate many different harmonic frequencies. Signal types can be single phase AC, three phase AC, or DC.
Harmonic filters isolate harmonic current to protect electrical equipment from damage due to harmonic voltage distortion. They can also be used to improve power factor. The detrimental effects of harmonic distortion can be manifested in many different ways, such as increased heating effect on electrical distribution equipment and cables, electronics miss-timings (computers, fax machines, etc.), capacitor overloads, fluorescent light flickering, and others.
Important general specifications to consider when searching for harmonic filters include the type and the signal type. Filter types include passive or active. Passive harmonic filters are built with a series of passive components such as resistors, inductors and capacitors. Passive filters are most common and available for all voltage levels. They are built-up by combinations of capacitors, inductors (reactors) and resistors. Active filters are available mainly for low voltage networks. Active harmonic filters are very fast electronic devices that will insert negative harmonics into the network, thus eliminating the undesirable harmonics on the network. The filters are built with active components such as IGBT-transistors and can eliminate many different harmonic frequencies. Signal types can be single phase AC, three phase AC, or DC.
Important performance specifications to consider when searching for harmonic filters include THID, rated power, standard compliance, nominal input voltage, and frequency. THID is the total harmonic current distortion of a signal is defined as the ratio of the sum of the powers of all harmonic frequencies above the fundamental frequency to the power of the fundamental frequency. Reactive power is defined as the mathematical product of voltage and current consumed by reactive loads. Examples of reactive loads include capacitors and inductors. These types of loads when connected to an ac voltage source will draw current, but since the current is 90o out of phase with the applied voltage they actually consume no real power in the ideal sense. Choices for standard compliance include IEEE 519, EN 61000, AS 2279, and BS G5/3. Nominal input voltages include, 110 V, 208 V, 240 V, 380 V, 480 V, and 600 V. Frequency choices include 50 Hz and 60 Hz.
Features common to harmonic filters include UL listing marks, performance monitors, operating temperature considerations, and form factor. The UL listing mark denotes that Underwriters Laboratories Inc. (UL) has found that samples of the product met UL's safety requirements. These requirements are primarily based on UL's published Standards for Safety. Performance monitors include indicators or meters to monitor certain device performances: Current THD, Voltage THD, Power, etc. Choices for form factor include NEMA 1 enclosure, NEMA 2 enclosure, NEMA 3 enclosure, NEMA 4 enclosure, NEMA 3R enclosure, NEMA 12 enclosure, rack mounted, and panel mounted.
