Variable Speed Drives, The Advantages of DC Chokes vs AC Line Reactors

[AtakanO]

     Most low-power drives have a very simple AC to DC input converter based on an
input diode rectifier and DC bus capacitors to reduce the DC voltage ripple. This
topology leads to input current harmonics that increase the RMS value of the input
current.
     To maximize energy efficiency or to meet the requirements of applicable
standards, some applications require reduction of the total harmonic distortion
(THD) of the drive’s input current.
     Many solutions exist that make use of passive components or active systems. This
data bulletin describes the differences between AC line reactors and DC chokes
when used in combination with variable speed drives to reduce the mains input
current’s THD. Total harmonic distortion of the current is called THDi in this
document.