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March 2023 – Factors to consider when selecting passive harmonic filters

Six quick ways to identify the passive harmonic filters suitable for your application

Enerdoor FINHRM5C yellow and silver passive harmonic filters

Harmonic filters work to isolate harmonic current and protect electrical equipment from damage due to harmonic voltage distortion. Often referred to as THD (total harmonic distortion) is the measurement of the harmonic distortion in a signal. Engineers use harmonic filters to mitigate the damaging effects of harmonic distortion which can include increased heating on electrical distribution equipment, capacitor overloads and miss-timings on electronics.


Passive Harmonic Filters

Passive harmonic filters are the most common form of harmonic filters and are built with a series of passive components including resistors, inductors and capacitors. Passive harmonic filters are used for all voltage levels making them suitable for a wide array of applications, whereas active harmonic filters are commonly used in low-voltage networks and are built with active components such as IGBTs.

There are numerous elements to consider when choosing a passive harmonic filter suitable for your application.

Six factors to consider when selecting passive harmonic filters

  • Filter size
  • Current THD
  • Power loss performance and operating temperature
  • Industry certifications and approvals
  • End application
  • Manufacturer expertise

Enerdoor’s advanced passive harmonic filters are available with excellent attenuation of current harmonic distortion and overvoltage spikes. The FINHRM5C filter features a compact size and is one of the smallest passive harmonic filters in the industry, taking up less cabinet space than any other filter on the market. Enerdoor’s FINHRM5C carries international compliance with IEEE-519 and IEC61000-3-12 harmonic standards. Enerdoor’s filters also carry UL approval for US and Canada, has support applications up to 1400A and reduces current THD to <5% with an unbalanced voltage of 2.5%.

Enerdoor’s range of passive harmonic filters offers less power loss than similar products on the market, which ensures lower temperatures inside the cabinet, resulting in decreased heat dissipation and energy costs.

Enerdoor’s FINHRM5C Passive Harmonic Filters


  • Small and compact size
  • Reduces current THD >5% with an unbalanced voltage of 2.5%
  • Rated current from 10A to 1400A
  • Rated up to 690Vac for the high voltage version
  • Enclosure options available – NEMA 1 and 3R



  • UL approved for USA and Canada
  • Compliant for international standards IEEE-519 and IEC61000-3-12
  • Low power loss and operating temperature
  • Reduces system loss from harmonic distortion
  • Remains unaffected by network conditions



  • VFDs and servo drives
  • Processing and industrial automation
  • Water and wastewater
  • Oil and gas
  • HVAC systems
  • SCRs (silicon-controlled rectifiers)

GD Rectifiers is the UK’s exclusive distributor for Enerdoor’s wide range of harmonic filters, Active harmonic filtersDC EMI filters, line reactors, motor protection, parallel filters, power factor correction, surge arresters and voltage stabilisers.

For further information on Enerdoor products, please call GD Rectifiers on 01444 243 452 or email

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Enerdoor FINHRM5C yellow and silver passive harmonic filter