Moeller PS 4 Guía de instalación
EMC Engineering Guidelines
For Automation Systems
PS 4
PS 416
04/97 AWB 27-1287-GB
1st edition 04/97
© Moeller GmbH, Bonn
Author: Werner Albrecht
Editors: Klaus Krüger, Thomas Kracht
Translator: Chris Baker, Terence Osborn
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04/97 AWB 27-1287-GB
Contents
1 Fundamentals of Interference-Free Design 3
General comments 3
Low-impedance connection 4
2 Construction of Reference Potential
Surfaces 5
Control cabinet design 5
Mounting plates, CI distribution boards 7
Fitting top-hat rails 8
Use of screened cables 9
Incoming external screen cables 10
Inter-building wiring system:
screening the line 12
3 Earthing Devices 13
PS 4 compact PLCs 13
PS 416 series of modular PLCs 16
Avoiding RF interference signals, ferrite ring 17
4 Installing a Screen Line Inside a
Control C abinet
19
PS 4 compact PLCs 19
PS 416 modular PLCs 20
5ESDMeasures 23
6 Lightning Protection 25
7 Accessories for Interference-free Design 27
Index 29
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04/97 AWB 27-1287-GB
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04/97 AWB 27-1287-GB
1 Fundamentals of Interference-Free
Design
General comments In order to meet EMC requirements the wiring of
systems using the PS 4 and PS 416 must observe
certain rules:
In particular a uniform reference potential must be
created.
The reference potential is formed by the totality of all
conductively interconnected, inactive metal
structures:
Control cabinet
Cabinet door(s)
Support bars
Mounting plate
Top-hat rail
etc.
Here you should ensure that there is a low-impedance,
conductive connection between all inactive metal
structures.
The following sections will show you the right way to
design your wiring systems.
The following rules must always be observed when
installing cables :
Cables should be grouped by function and then
routed so that they are kept spatially separated.
Cables with different functions should not be run
in parallel.
Power cables and signal or data lines should be
kept at least 10 cm apart.
Fundamentals of
Interference-Free Design
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04/97 AWB 27-1287-GB
Low-impedance
connection
A low-impedance connection is achieved in the
following way:
A large-area, low-impedance metal-to-metal
connection
The use of flexible earthing strips
Short connecting wires with a large surface area
and contact surface
In the case of enamelled, anodized or insulated metal
parts remove the insulating layer in the vicinity of the
connecting point. Protect the connecting points
against corrosion (for example, by greasing.
Important: use only suitable lubricants).
The connections of the reference surfaces should
comply with the pertinent regulations.
A conventional PE conductor with a small cross-
section will not be adequate.
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04/97 AWB 27-1287-GB
2 Construction of Reference Potential
Surfaces
The construction of the reference potential surfaces
is described below - from control cabinet design
through to connecting up equipment.
Control cabinet design The control cabinet housing is a part of the reference
potential surface.
To be sure that you have an adequate reference
potential surface you will need to observe the
following rules:
Construction of Reference
Potential Surfaces
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04/97 AWB 27-1287-GB
Figure 1: Installation
햲Connect all inactive metal parts (cabinet doors,
side parts and so on) to the reference potential
surface ensuring you have a large area and low
impedance connection.
햳Connect mounting plates together so that they
then form a common reference potential surface.
햴Make a large-area low-impedance connection
between the protective conductor bar and the
reference potential surface (cabinet housing).
햵Connect the guard screen of the screened cables
to the reference potential surface using a suitable
fastener (cable clip) and making sure the
connection is large-area and low-impedance. The
햲
햳
햴
햵
햶
Mounting plates,
CI distribution boards
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04/97 AWB 27-1287-GB
cable clip must sit snugly around the entire
circumference of the cable screen.
햶Connect the external protective circuit (potential
to earth) to the control cabinet reference potential
(internal protective conductor bar) with a large-
area and low-impedance connection.
Mounting plates,
CI distribution boards
You should use mounting plates as your base.
Connect the mounting plates to the control cabinet
with a low-impedance connection.
Use mounting plates made of galvanized sheet steel
(no enamelling).
The CI distribution board must be fitted with a
galvanized mounting plate. The mounting plate of the
CI distribution board forms the reference potential
surface.
Make sure that connecting points are protected
against corrosion.
Mounting plates must be connected not only to each
other but also to the internal protective circuit with
low-impedance and large-area connections so as to
form one overall reference potential surface. Here
you should connect the mounting plates, mounting
sub-plates, metal device plates to the cabinet
earthing system as often as possible.
Protect the all chassis earth connections against
corrosion.
Total insulation is cancelled by implementing the
provisions of “Reference potential surface”.
Construction of Reference
Potential Surfaces
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04/97 AWB 27-1287-GB
Figure 2: Large-area connections
햲Divided mounting plates as a whole are inactive
metal parts and thus form a constituent part of
the reference surface. This is why they must also
be connected together with low-impedance
connections (for example, using galvanized
earthing strips).
Fitting top-hat rails Fasten the top-hat rail to the mounting plate with a
large-area and low-impedance connection.
햲
Carrier rail
Mounting Plate
Use of screened cables
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04/97 AWB 27-1287-GB
Use commercially available top-hat rails that are
corrosion-proofed.
Figure 3: Fastening the top-hat rail
Use screws or rivets for a large-area and low-
impedance connection of the top-hat rail with the
support system.
In the case of enamelled, anodized or insulated metal
parts remove the insulating layer in the vicinity of the
connecting point. Protect the connecting points
against corrosion (for example, by greasing.
Important: use only suitable lubricants).
Use of screened cables The following wires or cables must always be
screened:
Communications lines
Analog lines
Counter lines
Inter-building data or signal lines (lightning
protection) and so on.
Carrier rail
Mounting plate
Top-hat rail
Top-hat rail
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