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July 2022 – How harmonics can reduce running costs

Published on: 27/07/2022

Introducing Enerdoor’s range of harmonic filters

Three Enerdoor passive and active harmonic filters in a line

Engineers are constantly faced with excessive total harmonic distortion (THD) which can result in network disturbances and component failures resulting in higher energy costs.

Low-harmonic drives use IGBTs to convert the incoming AC power to DC. With the front end monitoring the waveform of the input current, shaping it to be sinusoidal and uses LCL filters to combat low-frequency disturbances of >5kHz caused by IGBT switching. THD frequencies of up to 500kHz are managed using EMI-RFI-EMC filters which is often comparable to six-pulse drives.

Power quality is a major concern for today’s manufacturing and power generation facilities, finding the right solution for unbalanced loads is important and the two main power quality issues that engineers face are harmonic distortion and reactive power generated by a low power factor.

Passive Harmonic Filters

Passive harmonic filters and line reactors are recommended for single drive applications and are sized by the total current, they reduce THD and offer significant cost savings.


Active Harmonic Filters
Active harmonic filters work in parallel and compensate current for single or multiple load applications operating under varied loads. They may be used for single applications or for an entire facility. GD Rectifiers partners with Enerdoor to offer customers a broad range of harmonic solutions, including exclusive access to Enerdoor’s industry-leading passive harmonic filters, active harmonic filters and line reactors.


Benefits of Enerdoor’s Harmonic Solutions

  • Reduce harmonic distortion to >5% with an unbalanced voltage of 2.5%
  • Limit distortion within a certain level to mitigate effects on other equipment
  • Passive harmonic filters for drive applications and line reactors are sized by total current
  • Active harmonic filters work in parallel and compensate for load applications
  • Harmonic solutions are suitable for single applications or an entire facility

Harmonic filters are used becoming increasingly popular in protecting VFDs, servo drives, LED light drivers and other devices that rectify AC to DC and generate harmonic distortion. It’s important for engineers to limit the harmonic distortion in order to reduce damaging effects on other equipment within a facility.

As with any system, it is crucial to understand the complete set of components required and not just the individual filters alone. For systems where maintenance, running costs and space are an issue, passive harmonic filters offer a practical, reliable alternative to older technologies and ensure that harmonics will not disrupt your application.

For further information on Enerdoor’s passive harmonic filters or to discuss your requirements with our team, please call 01444 243 452 or email

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