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Advantages of 6-Pulse VFD with Lineator vs Active Front End (AFE) Drives


Active Front End (AFE) Drive manufacturers claim that their technology provides the best solution for the treatment of harmonics associated with variable frequency drives. They are quick to point out the benefits over standard 6-pulse VFDs equipped with diode bridge rectifiers, but what they won't tell you is that current harmonics are much higher when measured above the 50th, and that serious problems can result from introducing these higher frequency harmonics.

Why read this whitepaper?

The paper compares the two harmonic mitigation technologies in detail, and outlines a number of key reasons why AFEs are not the best solution for a low harmonic VFD. While AFEs do reduce the low frequency harmonics introduced by the VFD, they do so with negative consequences including:

  • high levels of high-frequency harmonics
  • an input-passive LCL filter that performs poorly and can resonate with the power system
  • much higher losses
  • increased complexity, which reduces reliability
  • significantly higher costs

The paper also explains that combining a Lineator AUHF Wide Spectrum Filter with a simple 6-pulse VFD is a much more efficient solution with the following advantages:

  • no high frequency harmonics
  • higher efficiencies
  • improved reliability
  • lower installation and operating costs