Line and load reactors are current-limiting, inductive devices used to remove distortion and filter power. Sometimes called line chokes, line and load reactors are commonly used in electronic variable speed drives where they provide an extra margin of protection to AC and DC drives from supply transistors.
Filter type and signal type are important specifications to consider when searching for line and load reactors. There are two choices for filter type: passive and active. Passive filters are built with a series of passive components such as resistors, inductors and capacitors. These devices are the most common type of line and load reactor filters, and are available for all voltage levels.
Active filters are used mainly in low-voltage networks. These line/load reactors are very fast electronic devices that insert negative harmonics in order to eliminate undesirable harmonics from a network. Active filters are built with active components such as insulated gate bipolar transistors (IGBT). They can eliminate many harmonic frequencies. Choices for signal type are single-phase AC, three-phase AC, and DC.
Performance specifications for line and load reactors include THID and rated power. A signal’s total harmonic current distortion (THID) 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. Rated power or reactive power is 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; however, since the current is 90 degrees out-of- phase with the applied voltage, they actually consume no real power in the ideal sense. Nominal input voltages for line and load reactor include 110 V, 208 V, 240 V, 380 V, 480 V, and 600 V. Frequency choices are 50 Hz and 60 Hz.
Features for line and load reactors include UL Marks, performance monitors, operating temperature, and form factor. The UL Mark denotes that Underwriters Laboratories Inc. (UL) has found that the line and load reactors met UL's published standards for safety. Line and load reactors with performance monitors have indicators or meters that monitor variables such as current THD, voltage THD, and power. 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.