Wiring and Shielding
© Siemens AG, 2004. All rights reserved
6-38 EMC Installation Guideline – Planning Guide (EMV) – 03.2004 Edition
Cable intercept bus
The cable intercept bus is necessary for the strain relief of the cables and lines. In
the following picture, two possible forms of strain relief can be seen.
Fig. 6-1 Strain relief by comb bus and cable intercept bus
Connection of the shield
The shield should be placed directly after the entry of the line into the cabinet onto
a shield bus and additionally routed up to the assembly. Screwing the plug to the
component housing via the product-specific, ready-made lines ensures the shield
contact.
Fastening of the shielding braid
For the fastening of the shielding braid to the cabinet housing, cable clamps of
metal are preferably to be used. The clamps must enclose the shield extensively
and ensure a good contact.
6.2.2 Basic rules for the shield connection of simple shielded lines
Double-sided shield connection
The line shield must be connected basically at both ends via extensive conduction
to the housing Only so the shield is also effective against high-frequency
interferences.
If external devices are connected to the controls for service or commissioning
purposes (printer, programming devices, PCs, etc.), their line shields must also
have a double-sided shield connection. It must be calculated with interference
couplings with a single-sided shield connection.
K1
K2
Shield connection
(large scale)
Fig. 6-2 Double-sided shield connection
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