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IAEI Magazine | Author: Tony Hoevenaars
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Tony Hoevenaars

Tony Hoevenaars is vice president of MIRUS International Incorporated, which specializes in the treatment of power system harmonics. Prior to joining MIRUS in 1996, Tony was the chief facilities electrical engineer at an IBM manufacturing facility in Toronto where he gained extensive experience in solving power quality related problems, particularly in the area of harmonics. Tony is a professional engineer, member of IEEE and has published various papers on power quality.


3rd Harmonic Blocking Filter: Is the Cure Worse Than the Disease?

It is commonly known that conventional transformers and neutral conductors can become overloaded and hot due to harmonics generated by computer equipment and other non-linear loads. Triplen current harmonics (mainly 3rd and 9th) sum arithmetically in the neutral and circulate in the primary windings of transformers. A simple and effective solution being commonly applied is to use K-rated, or more preferably, harmonic mitigating transformers and to double the ampacity of the neutral conductor. This prevents overheating without introducing negative side effects. Third harmonic blocking filters, on the other hand, reduce neutral current by preventing loads from drawing 3rd harmonic current. They will eliminate neutral conductor and transformer overheating but introduce NEC concerns and the potential for serious power quality issues.