Moeller PS 4 Installation guide

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

1
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

2
04/97 AWB 27-1287-GB

3
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
4
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.

5
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
6
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
7
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
8
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
9
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

Construction of Reference
Potential Surfaces
10
04/97 AWB 27-1287-GB
The cable screen must be earthed as close as
possible to the system's source of interference.
Always connect both ends of the cable screen to
potential to earth. Do not forget here that the
potential to earth may have different potentials at the
earthing positions.
In this case you will need to install a supplementary
equipotential bonding conductor with a cross-
section of 10 mm2.
Incoming external
screen cables
Connect the incoming screen cable to the local
reference potential surface. Make this connection
immediately after entry of the cable into the syste
(control cabinet, frame, mounting plate).
The following contact paths are possible:
햲Clamp strap  snap-on mounting  top-hat rail  reference potential surface
햳Contact clamp  snap-on mounting  top-hat rail  reference potential surface
햴Contact clamp  screwed connection to the busbar  reference potential surface
햵Clamp strap  screwed connection to the busbar  reference potential surface
Caution!
The cable screen must not be used for
equipotential bonding.
The exposed ends of the cable should be kept as
short as possible!

Incoming external screen
cables
11
04/97 AWB 27-1287-GB
Remove the insulation of screened lines at the
contact point. Make sure that the screen braid does
not get broken or damaged.
It is important that the connection of the busbar with
the reference potential surface is short and of low
impedance (no insulated segments)!
Top-hat rail 햲햳
Busbar 햴햵
Top-hat rail
Busbar
M4
integrated
srew

Construction of Reference
Potential Surfaces
12
04/97 AWB 27-1287-GB
왘Make a new braided screen contact as close as
possible to the device.
Inter-building wiring
system:
screening the line
For lightning protection in accordance with
ENV 50 142 you should use a suitable surge arrester.
Surge arresters manufactured by Messrs Dehn, for
example, are suitable here.
All inter-building wires and cables must be screened.
The screenscreen must not be used as a
equipotential bonding conductor as it does not have
the requisite current-carrying capacity.
For signal lines you should install suitable
overvoltage protective devices.
These protectors should be fitted wherever possible
at the point where the cable enters the building, but
never later than the control cabinet.
Inter-building lines which are included in the
equipotential bonding will need to be routed within
metal conduits. These metal conduits must then be
earthed at both ends.
The minimum cross-sections of the lighting
protection equipotential bonding conductors
specified by IEC 61 024-1 are as follows:
16 mm2copper
25 mm2aluminium
50 mm2iron
With this kind of installation it is not necessary to
connect the screen to the equipotential bonding.
In addition, with the first consumer in each case
following entry into the building you will need to
connect a blue surge voltage protector clamp
(secondary protector). Then earth the yellow and
green terminal of this clamp at the next earthing
position.

13
04/97 AWB 27-1287-GB
3 Earthing Devices
PS 4 compact PLCs Installation on top-hat rail
Figure 4: Device earthing when installing on top-hat rail
햲Top-hat rail
햳Functional earthing (with DC devices)
Protective and functional earthing (with AC devices)
햴Protective conductor bar
햵Connection only with AC devices
햶Protective conductor clamp
DC devices:
Connect the functional earthing to the reference
potential surface as short as possible with a 2.5 mm
2
core cross-section via a protective conductor clamp
and top-hat rail –for example, from Weidmüller or
Phoenix.
AC devices:
Connect the protective and functional earthing to the
reference potential surface as short as possible with
a 1.5 mm2core cross-section via a protective
conductor clamp and top-hat rail –for example, from
Weidmüller or Phoenix. In addition the protective
24 V
0 V
PS4/EM4
햲
햴
햵
햳
N
L1
햶
DC devices
AC devices

Earthing Devices
14
04/97 AWB 27-1287-GB
earth should be connected as short as possible to
the protective conductor bar with a 1.5 m 2core
cross-section.
Installation on mounting plates
Figure 5: Device earthing when installing on mounting plates
햲Mounting plate
햳Cable lug
햴Functional earthing (with DC devices)
Protective and functional earthing (with AC devices)
햵Fixing feet
햶Protective conductor bar
햷Additional connection with AC devices, core cross-
section 1.5 mm2
DC devices:
Connect the functional earthing to the mounting
plate (reference potential surface) as short as
possible and with a 2.5 mm2core cross-section.
PS4/EM4
햲
햵
햳
햶
햷
24 V
0 V
NL1
햴
DC devices
AC devices

PS 4 compact PLCs
15
04/97 AWB 27-1287-GB
The conductor is connected to the mounting plate
via a highly conductive connection which should be
as flat as possible; for example, a cable lug.
Connect the fixing feet to the mounting plate with a
low-impedance connection.
AC devices:
Connect the protective and functional earthing to the
mounting plate (reference potential surface) as short
as possible and with a 1.5 mm2core cross-section.
The protective earth should also be connected as short
as possible to the protective conductor bar with a
1.5 mm2core cross-section.
The conductor is connected to the mounting plate
via a low-impedance connection which should be as
flat as possible; for example, a cable lug.
Connect the fixing feet to the mounting plate with a
low-impedance connection.

Earthing Devices
16
04/97 AWB 27-1287-GB
PS 416 series of
modular PLCs
Rack
You should connect the rack to the carrier system
(mounting plate, rack frame, hinged frame and so on)
with a low-impedance connection of maximum area.
Connect the rack to the protective conductor bar.
The protective earthing cable used here must have a
cross-section of 6mm
2.
The side panels of the rack have been designed to
include a connection for the protective earthing
cable.
Fix the protective earthing cable to the side panel
using a punched cable lug (of the correct size!) .
Figure 6: Earthing the rack
햲Protective earthing cable
햳Protective conductor bar
햲
햳

Avoiding RF interference
signals, ferrite ring
17
04/97 AWB 27-1287-GB
Avoiding RF
interference signals,
ferrite ring
If RF interference signals are to be avoided, when
installing the assemblies you will need to fit the data
lines –and possibly also the supply lines –with ferrite
rings.
Fit the ferrite ring directly below the potential
equalisation bar. If it is to function correctly the ferrite
ring must fit the cable snugly.
Use two cable ties at the cable to hold the ferrite ring.
After the ferrite ring there should not be any onward
runs to other devices.
Card Ferrite ring for supply
lin
Ferrite ring for data line
Power supply card PS 416-POW-400 
Power supply card PS 416-POW-420 
Digital output card PS 416-OUT-400 
Digital output card PS 416-OUT-410 
Counter card PS 416-CNT-200 
Communications card PS 416-NET-210 
Communications card PS 416-NET-220 
Communications card PS 416-NET-230 
Communications card PS 416-MOD-200 
Communications card PS 416-COM-200 

Earthing Devices
18
04/97 AWB 27-1287-GB
The ferrite ring is not included in the scope of supply
of the cards.
Figure 7: Fitting the ferrite ring
햲Cards
햳Ferrite ring P S416-ZBX-405
햴Cable ties
햵Screen connection
햶Screened data line
햷Supply line
햸Potential equalisation bar
햲
햸
햷
햶
햳
햵
햳햴

19
04/97 AWB 27-1287-GB
4 Installing a Screen Line Inside a
Control C abinet
PS 4 compact PLCs
Figure 8: Screen connection to reference potential surface
햳
햴
M 44/EPS
0 V
V24
M4
햲