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LPF Series Solutions

LPF Series Solutions

LPF Series Solutions
(Type LPF) 200-690 volts 50/60hz

APPLICATION: Three Phase Low Pass Harmonic Filters are ideal for both commercial and industrial equipment such as variable frequency motor drives, pumps, fans, compressors, chillers, conveyors, cranes and many other types of electronic controls. Our Type KS version achieves harmonic current distortion levels at or below 5% THD-i and complies with IEEE-519 and other international power quality standards. May be used to filter harmonics for one or more variable frequency drives.

Two Choices: Three Stage Filter (KS) Version and Two Stage Filter (KB) Versions

  • Three Stage Filter (Type KS)

    Three stage filter that significantly reduces 5th -51st harmonics, achieves 5% THD-i and brings AC variable frequency drive systems into compliance with international power quality standards including IEEE-519. Use with virtually any 6-pulse AC variable frequency drive to achieve the lowest possible levels of harmonic distortion at all operating conditions from 0% to 100% load. KS version filters may also be used to reduce harmonic distortion in DC drive systems.

  • Two Stage Filter (Type KB)

    Two stage filter that reduces 5th -51st harmonics to low levels and helps to bring AC variable frequency drive systems into compliance with limits for harmonic distortion. This economical low pass harmonic filter relies upon inductance within the VFD to serve as a third stage of filtering to achieve low levels of harmonic distortion.

1. Type KS Standard Version
3-Stage Filter
  2. Type KB Basic Version
2-Stage Filter

Use our standard (Type KS) Low Pass Harmonic Filter, to achieve 5% THD-I for 6-pulse drives.


Use our basic 2-stage filter (Type KB) to meet 5-8% THD-I when taking advantage of internal VFD inductance. Type KB filters may also be used w/o internal VFD inductance when THD-I limit is 8-12%.

KS Standard 3-Stage Filter Diagram   KB Basic 2-Stage Filter Diagram

  Typical Performance
3-Stage (KS) and 2-Stage (KB)
  Low Pass Harmonic Filter  

Typical Distortion Levels for Various Harmonic Mitigation Techniques
without Internal Reactor
with 3% Internal Reactor
with 5% Internal Reactor
DC Drive
KS Version ≤ 5% THD-i ≤ 5% THD-i ≤ 5% THD-i Varies by speed and load
KB Version Varies by system 8-12% THD-i 5-8% THD-i Varies by speed and load
5% Line Reactor 35% THD-i 28% THD-i 26% THD-i 25 - 40% THD-i
3% Line Reactor 45% THD-i 32% THD-i 28% THD-i 30 - 50% THD-i
Nothing 40-80% THD-i 45% THD-i 35% THD-i 40 - 60% THD-i