8800DB1705

Introduction

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.

AC line reactor

An AC line reactor is wired at the drive’s mains inputs.

AC line reactor wiring

DC choke

A DC choke can be split into two chokes, as shown in Figure 2, or kept as one part located in either the DC+ or DC- line of the drive.

DC choke wiring

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