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Power quality, harmonics: How to select a variable frequency drive (VFD)

May 15, 2024

Pumping, compressing, blowing, conveying, extruding and mixing are among most common industrial motor applications using variable frequency drives (VFDs). Understanding applications and drive design can help mitigate harmonics and power-quality challenges. As explained in part 1, when motors are started across the line on 60Hz utility power, efficient motor operation is limited to a very narrow window around the rated motor operating speed and torque values. Drives allow motors to operate at their optimal efficiency over a wide range of speeds, satisfying a wide range of varying torque requirements, while reducing motor stress and starting inrush current.

Learning Objectives

  • Review variable frequency drive (VFD) fundamentals and how a VFD works on the way to understanding how non-linear loads create power-quality concerns.
  • Understand harmonic filtering and how a VFD can help.
  • Examine medium-voltage 36-pulse drive topology and how it reduces risk of equipment malfunction by reducing harmonic stress.

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