Grounding Of Shielded Control Cables - Danfoss VLT FC 102 Series Design Manual

Electrical Installation

6.8.3 Grounding of Shielded Control Cables

Correct shielding
The preferred method in most cases is to secure control
and cables with shielding clamps provided at both ends to
ensure best possible high frequency cable contact.
If the ground potential between the adjustable frequency
drive and the PLC is different, electric noise may occur that
disturbs the entire system. Solve this problem by fitting an
equalizing cable next to the control cable. Minimum cable
cross-section: 0.025 in
6 6
Figure 6.65 Control Cable with Equalizing Cable
1
Min. 0.025 in
2 Equalizing cable
Table 6.40 Legend to Figure 6.65
50/60 Hz ground loops
With very long control cables, ground loops may occur. To
eliminate ground loops, connect one end of the shield-to-
ground with a 100 nF capacitor (keeping leads short).
Figure 6.66 Shield-to-ground Connected to a 100 nF
Capacitor
132
Design Guide
2 2
[16 mm ].
PLC FC
PE PE
<10 mm
PE PE
1
2
2 2
[16 mm ]
PLC FC
PE
100nF PE <10 mm
Danfoss A/S © Rev. 06/2014 All rights reserved.
Avoid EMC noise on serial communication
This terminal is connected to ground via an internal RC
link. Use twisted-pair cables to reduce interference
between conductors.
FC
69
68
61
PE
PE
2
Figure 6.67 Twisted-pair Cables
1
Min. 0.025 in 2 [16 mm 2 ]
2 Equalizing cable
Table 6.41 Legend to Figure 6.67
Alternatively, the connection to terminal 61 can be
omitted:
FC
69
68
PE
PE
1
2
Figure 6.68 Terminal 61 not Connected
1
Min. 0.025 in 2 [16 mm 2 ]
2 Equalizing cable
Table 6.42 Legend to Figure 6.68
FC
69
68
61
PE
<10 mm
PE
1
FC
68
69
PE <10 mm
PE
MG11BC22