● When the cables are routed close to ground potential, the immunity to interference is
increased. For this reason, you are advised to lay these cables along edges and at ground
potential.
● Ground the reserve cores on at least one end.
● In order to avoid additional locations where interference can be coupled in, long cables
should be shortened or routed where there is little interference.
● If conductors or cables conduct signals of different classes, then the conductors and cables
must cross at a right angle. This especially involves sensitive and noisy signals.
– Class 1:
Unshielded cables for ≤ 60 VDC
Unshielded cables for ≤ 25 VAC
Shielded analog signal cables
Shielded bus and data cables
Operator panel interfaces, incremental/absolute encoder cables
– Class 2:
Unshielded cables for > 60 VDC and ≤ 230 VDC
Unshielded cables for > 25 VAC and ≤ 230 VAC
– Class 3:
Unshielded cables for > 230 VAC/VDC and ≤ 1000 VAC/DC
– Class 4:
Unshielded cables for > 1000 VAC/DC
Shield connection
● Do not use cable shields to conduct current. In other words, cable shields must not
simultaneously act as neutral or PE conductors.
● Apply the cable shield so that it covers the greatest possible surface area. Use ground
clamps, ground terminals or ground screw connections.
● Avoid extending the cable shield to the grounding point via a wire. This reduces the shield
effectiveness by up to 90%.
Electrical connection
6.2 Electromagnetic compatibility
SINAMICS SM120 6SL38715
68 Operating Instructions 07/2015
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