Emc Compatible Installation Of Plc - Siemens SIMATIC S7-300 Hardware And Installation Manual

see also
Grounding concept and overall structure
Shielding of cables
Outdoor cable routing
Cable routing inside buildings

EMC compatible installation of PLC

12.2.3 EMC compatible installation of PLC
Introduction
Quite often it is the case that interference suppression measures are not taken until
corruption of user signals is detected after the controller is actually in operation.
Frequently, the causes of such interference are found in inadequate reference
potentials as a result of faulty installation. This section shows you how to avoid
such errors.
Inactive metal parts
Inactive parts are referred to as electrically conductive elements, separated from
active elements by a basic insulating and only subject to electrical potential if an
error occurs.
Installation and ground bonding of inactive metal parts
Bond all inactive metal parts to a large-surface ground when you install the S7-300.
Proper ground bonding ensures a homogeneous reference potential for the
controller and reduces the effect of interference coupling.
The ground connection establishes an electrically conductive interconnection of all
inactive parts. The sum of all interconnected inactive parts is referred to as chassis
ground.
This chassis ground must never develop a hazardous potential even if a fault
occurs. Therefore, chassis ground must be connected to the protective conductor
using cables with an adequate conductor cross-section. To avoid ground loops,
physically separate chassis ground elements (cabinets, parts of the building
construction or machine) must be bonded to the protective conductor system in a
star circuit.
S7-300 Programmable Controller Hardware and Installation
A5E00105492-02
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Appendix
12-7