Chapter 5 Solution To Emi: Filter; Filter - Delta CP2000 Series User Manual

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.
Chassis Grounding
Connect to the steel
structure of the building

Chapter 5 Solution to EMI: Filter

The Shielded
Chassis
EMI Filter
R/L1
L1 L1'
S/L2
L2 L2'
T/L3
L3 L3'
IP20/NEMA 1/UL Type 1
Metal Conduits
Shielded Motor Cable
12
Option Kit
U/T1
V/T2
W/T3