Delta Electronics VFD037CH23A-21 — устранение помех и гармоник в аналоговых входных сигналах [637/638]

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Analog Input Signals

If the analog input signals are affected by noise from the AC motor drive, please connect a capacitor and

a ferrite core as indicated in the following diagram.

Wind the wires around the core in same direction for 3 times or more.

AVI/ACI/AUI

ACM

Ferrite core

5.2 Harmonic Interference

The AC motor drive’s input current is non-linear, the input rectifier generates harmonics. Harmonics must

be limited to within a certain range to avoid impact the mains power and to avoid current distortion to

ensure surrounding devices are not influenced. An AC Motor Drive with built-in DC reactor suppresses

harmonic currents (Total Harmonic Current Distortion THID) effectively and therefore reduces the

harmonic voltage peaks (Total Harmonic Voltage Distortion).

Harmonic Current at the Power Supply Side

(A) Fundamental Sin e Wave

(6 0Hz )

(B) Ha rmonic

(1 80H z)

Di sto rte d Wave

(B) Harmonic

(3 00H z )

Distorted Wave

(A) Fundamen tal Sine Wave

(6 0Hz )

Suppression of Harmonic Currents

When a large portion of lower order harmonic currents (5

, 7

, 11

th ,

etc) occur at the power input,

surrounding devices will be disturbed and the power factor will be low as a result of reactive power.

Installing a reactor at the AC Motor Drive’s input effectively suppresses lower order harmonic currents.

AC Reactor

Installed in series with the power supply and is effective in reducing low order current harmonics.

Features of an AC reactor include:

1. Reduces the harmonic currents to the AC Motor Drive and increases the impedance of the power

supply.

2. Absorbs interferences generated by surrounding devices (such as surge voltages, currents, and

mains surge voltages) and reduce their effect on the AC Motor Drive.

3. Increases the power factor.