Harmonic Filters for Reducing VFD Distortion


VFDs create harmonic distortion. Any VFD using a bridge rectifier inherently draws harmonic current from the utility. The harmonic current draw causes voltage distortion on the mains which can create power quality issues for other electrical loads.


KEB Harmonic Filters are used to reduce VFD distortion and meet IEEE 519 distortion levels. Using a harmonic filter with a VFD reduces the amount of harmonic current, therefore, the voltage distortion on the mains is reduced.


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Electrical loads like resistors and line fed induction motors draw a sinusoidal current from the supply.


Most commercial VFDs use a 6-pulse bridge rectifier to convert from AC to DC power.  6-Pulse inverters draw a non-sinusoidal input current which then creates distortion on the supply voltage.


The voltage distortion is undesirable because it can negatively affect the operation of other electrical loads.


Critical applications using VFDs like wastewater treatment plants, elevators, and airports might need to mitigate harmonic distortion.  There are a number of ways to address harmonics, but harmonic filters strike a good balance between performance and cost.


KEB’s Z1 (zee-one) Harmonic Filters are designed to meet IEEE (eye-triple-E) 519 (five-nineteen) harmonic levels.  The filters are offered in graduated sizes up to 400Hp.


In order to achieve the best possible performance, KEB offers filters for different electrical mains around the globe.  Filters are available for both 230V and 480Vac mains.  Additionally, filters optimized for both 50Hz and 60Hz mains are offered.


KEB Filters are intended to be used for demanding industrial VFD applications and feature a 150% current overload rating for 60 seconds.


As standard, the units feature overload protection and temperature sensors for the filter windings.


The Z1 filters are 99% efficient at full load.  This is achieved through the use of high quality steel laminations and winding configuration.


KEB’s Z1 filters feature high-performance 3-phase capacitors for increased operating lifetime and reliability.


The harmonic filters use a compact design and flexible mounting concept.  The capacitor bank can be mounted separately from the core – up to 2 meters apart.  This allows a machine builder to flexibly position and mount the components inside an enclosure.


As an option, the large filters are offered in a pre-wired NEMA1 enclosure.


KEB Harmonic filters are UL listed and carry a CE mark to ensure the highest quality and performance.



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