I've been studying for a while now topics related to power quality issues, such as harmonics caused by non-linear loads and power converters, and I've been working on Active Power Filters, but since I live in developing country sadly all we have is theoretical knowledge, So I appreciate if you add any professional knowledge to those conversation.

  1. What is the commercial name of an active power filter (if I write that under electronics in Amazon, it doesn't give me any result)
  2. Same question goes to Unified Power Quality Controller ? (I can't find those in Amazon too)
  3. What are the main manufacturers of those devices in the world?
  4. Could you recommend any good readings about this topic to have an idea about the industrial and marketing field
  • $\begingroup$ Uninteruptible Power Supply $\endgroup$ – Solar Mike Mar 24 '18 at 16:41
  • $\begingroup$ At first I thought that too, but UPS only backup the power supply, they don't do active compensation, harmonic mitigation and waveform enhancement (lower the THD) ! so you can't consider UPS as APF ! $\endgroup$ – Carter Nolan Mar 24 '18 at 16:50
  • $\begingroup$ The big 13.5kVA 3 phase one I collected for free isolated the mains input from the mains output totally unless you switched it into maintenance mode... so it provided quality sine wave power at all times : had 130 computers plus other electronics on it, but up to you. $\endgroup$ – Solar Mike Mar 24 '18 at 16:53
  • $\begingroup$ Excuse me if my comment was harsh, didn't mean any disrespect toward you, but the theoretical stuff i studied states that UPS are not active power filters, and may be i'm wrong and honestly this is what i struggle with ! thank you for your answer again. $\endgroup$ – Carter Nolan Mar 24 '18 at 17:27

I have procured "active harmonic filters" for an engineering project. We needed them to compensate for the harmonics caused by a large number of variable speed drives.

Active harmonic filters are not a consumer product, so you won't find them on Amazon.

Try looking in the catalogues of Danfoss or Siemens, who are two manufacturers of these type of units. Other manufacturers of VSDs, i.e. ABB, are also likely to offer an active harmonic filter.


An UPS can be used for filtered power but if still hum/harmonix /.... you can use an Op-Amp as a 'Notch' filter to filter out undesirable frequencies

  • 1
    $\begingroup$ Please read this to improve the quality of your posts. $\endgroup$ – peterh Mar 25 '18 at 16:22
  • $\begingroup$ An Op-Amp e.g. IC741 can be used with capacitive feedback at right selectected frequency as a 'Notch Filter' but to drive high current, I am not sure , you can try some power Inverters based on Power MOSFET/... devices as an inverter to filter out frequencies. $\endgroup$ – srikanthsp Apr 6 '18 at 5:58

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