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Line Reactors - Diagrams and Applications

Line Reactors
A line reactor absorbs many of the power line disturbances which otherwise damage or shut down your inverters, variable speed controllers, or other sensitive equipment. Line Reactors are the modern technology solution to inverter and drive application problems. Many of the AC reactors are harmonic compensated and IGBT protected to assure optimum performance in the presence of harmonics. These reactors are very effective at reducing harmonics produced by inverters and drives, and in most cases. Harmonic compensated line reactors are used on either the input or output of an adjustable speed drive/inverter.
Line Reactors are available in 1 - 250 horsepower with 208, 240, 480 and 600 voltage ratings at 60 Hz. It is always important to choose a variety of current options for 3% and 5% impedance. Keep in mind that Line/Load reactors are selected based upon motor horsepower and voltage ratings. Verify that the drive and motor continuous current rating is within the fundamental current rating of the reactor before making a final selection for the application.
Line Reactor Impedance Ratings
Line Reactor impedance rating formula
There are two types of impedance ratings to choose from in Line Reactors - three percent or five percent.
  • 3% impedance - reactors are usually sufficient to absorb power line spikes and motor current surges. They will prevent nuisance tripping of drives or circuit breakers in most applications. A 3% impedance line reactor is typical for the line side of a drive.
  • 5% impedance - reactors are best for reducing harmonic currents and frequencies. Use them when you must comply with IEEE 519, to reduce motor operating temperature, or to reduce motor noise. A 5% impedance line reactor is used mostly for the load side of a drive.
Applying Load/Line Reactors
Below are four of the most common applications for Line Reactors:
Line Reactor application diagrams
  • Input to Inverter/Drive: On the input side of an electronic motor speed controller, line reactors protect sensitive electronic equipment from electrical noise created by the drive or inverter (notching, pulsed distortion, harmonics). They also protect the controller from surges, or spikes on the incoming power lines, we well as reduce harmonic distortion. They help meet the requirements of IEEE 519.
  • Output of Inverter/Drive: In long motor lead applications, use reactors (IGBT protected) between the inverter and motor to reduce dv/dt and motor terminal peak voltage. The use of a load (output) reactor also protects the controller from a surge current caused by a rapid change in the load, and even from a short circuit at the load.
  • Multiple Controllers: Multiple drives or inverters on a common power line require one line reactor per controller. Individual reactors provide filtering between each controller (reduce crosstalk) and also provide optimum surge protection for each unit. A single line reactor serving several controllers does not provide adequate protection, filtering or harmonic reduction when the system is partially loaded.
  • Multiple Motors: When more than one motor is controlled by a single drive, a single line reactor can usually be used between the controller and the motors. The line reactor should be sized based on the total motor/load horsepower.
Line Reactor Video Overview
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