Why Should You Use a Line Reactor?

By Yin on 30th Jun 2014

Why do our engineers recommend line reactors?

After reading about How will line reactors help your VFD and What is a line reactor, you probably already have an idea how line reactors can help your VFD. Here are the reasons why our team of engineers at VFDs.com recommends line reactors:

  • Easy to add to an existing VFD
  • Provide surge protection for the VFD
  • Increased reliability and life span of the VFD
  • Provide some protection against over-voltage trips
  • A cost-effective solution to reduce harmonic distortion
  • Provide some buffering against voltage spikes
  • Bringing the facility into compliance with utility standards
  • Avoid litigation and damage settlements
  • Reducing the amount of high frequency noise injected into the power system.
  • Improving true power factor
  • Reducing cross-talk between drives
  • Prevent fuses and circuit breakers from blowing or tripping due to high current spikes
  • Provide needed impedance between VFD's and power system capacitors
  • Protection of capacitors and other power system components from harmonic resonance
  • Free up system capacity by reducing current levels
  • Reduce intermittent faults and problems of unknown origin

Our team of experienced engineers recommends that all variable frequency drives should include reactors, at a minimum, for control of harmonics and power system pollution. Line reactors are the commonly preferred method of harmonic correction due to their effectiveness, reliability, and low cost. AC line reactors, or a combination of ac and dc reactors, will provide enhanced surge protection in addition to harmonic mitigation. Typical AC line reactors are 3% to 5% impedance, with the 5% models offering better harmonic control and better surge resistance, but at a slightly higher cost when compared to their 3% counterparts.

Our patents on passive harmonic filters

IEEE 519 (IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems) is the harmonic standard that is universally used in determining acceptable limits for power system distortion. This standard allows from 5% to 20% Total Harmonic Current Distortion (THID) depending on the "stiffness" of the power system. The point at which this is measured is the Point of Common Coupling (PCC), which is the closest point on the utility side of the customer's service where another utility customer is or could be supplied. While the approximate 30% THID from a drive utilizing line reactors is greater than the allowable limits, the current is typically diluted by other cleaner loads within the facility, thus bringing the facility as a whole, into compliance. If this is not the case, there are other harmonic reduction techniques that can be brought to bear, but at a significantly higher cost than reactors.

Where reactors (35% THID) alone are insufficient, harmonic filters provide additional harmonic mitigation (12% or 15% THID). At VFDs.com, we offer a variety of enclosures where you can integrate line reactors, DC link reactors, or harmonic filters into the same enclosure.

VFDs.com is a division of Energy Management Corporation, which developed and held one of the original patents of the passive harmonic VFD filters through years of R&D by our P.H.D. level engineers. This technology was so innovative that it soon became widely used throughout the industry for harmonic distortion reduction. 

Line reactors features

As you know, AC line reactors applied to the line side of a VFD drive will improve THID and provide increased reliability and longevity. Our line reactors currently begin at $74.99. View our list of inventory here:

Shop our Line Reactors


  • Sizes from 1/2 HP to 1250 HP
  • 3 phase, 600V class
  • Available in 208/240, 480 and 575/600, 690 VAC
  • 50/60 Hz
  • 1.5% or 3% Impedance (Low Z) and 5% Impedance (High Z) available
  • cUL, UL; UL Recognized, CE Marked
  • Universal mounting footprint
  • Enclosures: Open, UL Type 1, UL Type 3R
  • Warranty: From installation to the permanent failure of the VFD