Harmonic filter resistors (also known as damping resistors) are fundamental for reducing harmonic distortions, i.e., distortions in the frequency of the waves running through the electrical supply network. In industrial settings, these variations are often caused by the use of nonlinear loads, such as those associated with power electronic converters and arc furnaces. Harmonic distortions can cause voltage and current variations, which in turn can cause

  • Equipment heating and malfunctioning, especially in testing equipment
  • Interference and noise in communication systems, such as radios and phones
  • Insulation failure due to heating and voltage peaks higher than the rated fundamental voltage signal

Harmonic filter circuits prevent these issues from even arising by allowing standard frequencies to move through the grid while absorbing harmonic frequencies. Those resistors are a crucial, passive component of such circuits. They dissipate the electric energy-related to harmonic waves as heat, thus removing it from the system.


They can be used in:

  • single-tuned harmonic filters
  • second order harmonic filters
  • high-pass harmonic filters
  • C-type harmonic filters

This depends to the type of load and purpose.


Fairfild’s develops many custom harmonics filter resistors, based on the specific needs of clients, but it also has a wide array of off-the-shelf versatile resistors available. All of Fairfild’s harmonic filter resistors are characterized by:

  • low variation of resistance value at high temperatures
  • low working overheating
  • high reliability and insulation, even in the event of over-voltages