Siemens Automation System S7-400 - Manual (Page 179)

Assembling and Installing Systems
A-11
Automation System S7-400 Hardware and Installation
A5E00850741-01
Key for example 1
The numbers in the following list refer to the numbers in Figure A-2.
Table A-1 Key for Example 1
No. Key Meaning
1 Grounding strips If there are no large-area metal-to-metal
connections, you must interconnectinactive metal
parts such as cabinet doors or support plates via
grounding strips or to ground. Use short grounding
strips with a large surface.
2 Supporting bars Connect the supporting bars and the cabinet
housing over a large area (metal-to-metal
connection).
3 Secure the rack There must be a large-area metal-to-metal
connection between supporting barand rack.
4 Signal lines Use cable clamps on the protective ground bar or an
additional shield bus forlarge-area connection of the
shield of signal lines.
5 Cable clamp The cable clamp must surround the braided shield
over a large area and ensuregood quality contact.
6 Shielding bus Provide a large-area connection between the shield
bus and supporting bars (metal-to-metal
connection). The cable shields are connected to the
shield bus.
7 Protective ground
bar
Provide a large-area connection between the protec-
tive ground bar and supporting bars (metal-to-metal
connection). Connect the protective ground bar to
the protective conductor system via a separate con-
ductor (minimum cross-section 10 mm 2 ).
8 Conductor to the
protective conductor
system (grounding
point)
Provide a large-area connection between the
conductor and the protective conductor system
(grounding point).
Example 2: EMC--compliant Wall Mounting
If you operate your S7-400 in a low-interference environment in which the
permissible ambient conditions are complied with (see the Module Data reference
manual, Chapter 1), you can mount your S7-400 in frames or on the wall.
Picked-up interference must be given a path to large metal surfaces. You should
therefore secure standard mounting channels, shield, and protective ground bars to
metal structural elements. For wall mounting in particular, installation on reference
potential surfaces made of sheet steel has proved advantageous.
Provide a shield bus for connecting the cable shields if you install shielded cables.
The shield bus can simultaneously serve as the protective ground bar.