Delta CT2000 Series, User Manual

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Chapter 19 EMC Standard Installation Guide

CT2000 Series
19-16
19-5 Solution to EMI: Filter
19-5.1 Filter
Electromagnetic interference is transmitted in two ways, by radiation and by conduction. The most effective
and economical method of reducing radiated interference is to use shielding and of reducing conducted
interference is to use an electromagnetic filter.
Noise interference can be divided into two categories: high frequency (150kHz~300MHz) and low frequency
(100Hz~3000Hz). High-frequency noise fades more over distance and has a shorter wave-length, while low-
frequency noise fades less over distance and has a longer wave-length.. Both types of interference are transmitted
through power cables and power leads, affecting the power supply side.
High-frequency interference at the power side can be eliminated or attenuated by mounting a filter. The filter
consists of coils and capacitors. Some drives do not have a built-in filter, in which case the installation of an
external option filter is required. The drawing below shows a standard filter diagram:
A filter is composed of a Differential Mode section (to eliminate noise below 150kHz) and a Common Mode
section (to eliminate noise above 150kHz). For high-frequency noise , the inductor acts as a high impedance to
form an open circuit and the capacitor acts as a low impedance to form a short circuit. Proper design and
dimensioning of inductors and capacitors give a resonant circuit to absorb harmonic currents. Capacitor Cy is
earthed to lead the harmonic currents to the ground.
External Filter
The filter and the AC drive should be installed in the control cabinet or on the mounting plate that is earthed
to ground. The motor cable must be shielded and as short as possible. Please use the filters recommended by
Delta to ensure compliance with EMC standards.
EMI Filter
L1 L1'
L2 L2'
L3 L3'
R/L1
S/L2
T/L3
U/T1
V/T2
W/T3
Chassis Grounding
Connect to the steel
structure of the building
Shielded Motor Cable
Metal Conduits
The Shielded
Chassis
IP20/NEMA 1/UL Type 1
Option Kit