Earthing (Grounding) Of Screened Control Cables - Danfoss VLT FC 322 Instruction Manual

Installation VLT® Automation VT Drive FC 322 D-Frame Instruction Manual
2.5.3 Earthing (Grounding) of Screened
Control Cables
Correct screening
2 2
The preferred method in most cases is to secure control
and serial communication cables with screening clamps
provided at both ends to ensure best possible high
frequency cable contact. If the earth (ground) potential
between the frequency converter and the PLC is different,
electric noise may occur that will disturb the entire system.
Solve this problem by fitting an equalizing cable next to
the control cable. Minimum cable cross section: 16 mm
Figure 2.13
1 2
Min. 16 mm
2 Equalizing cable
Table 2.6
50/60 Hz earth (ground) loops
With very long control cables, earth loops (ground loops)
may occur. To eliminate earth (ground) loops, connect one
end of the screen-to-earth (ground) with a 100 nF
capacitor (keeping leads short).
Figure 2.14
2-12 MG21E122 - VLT® is a registered Danfoss trademark
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Avoid EMC noise on serial communication
This terminal is connected to earth (ground) via an internal
RC link. Use twisted-pair cables to reduce interference
between conductors. The recommended method is shown
below:
2
.
Figure 2.15
2
1 Min. 16 mm
2 Equalizing cable
Table 2.7
Alternatively, the connection to terminal 61 can be
omitted:
Figure 2.16
2
1 Min. 16 mm
2 Equalizing cable
Table 2.8