Shielded Cable Grounding - Danfoss VLT FC Series Service Manual

Operator Interface and Driv...

4.9 Shielded Cable Grounding

Connect the shielded control cables with cable clamps at both ends to the metal cabinet of the drive. Table 4.15 shows
ground cabling for optimal results.
Table 4.15 Shielded Cable Grounding
MG94A502
Service Guide
Correct grounding
Fit control cables and cables for serial communication with cable clamps at both ends to
ensure the best possible electrical connection.
Incorrect grounding
Do not use twisted cable ends (pigtails) since it increases shield impedance at high
frequencies.
Ground potential protection
When the ground potential between the drive and the PLC or other interface device is
different, electrical noise occurs that can disturb the entire system. Fitting an equalizing
cable next to the control cable resolves this issue. Minimum cable cross-section is 8.36
2
mm (8 AWG).
50/60 Hz ground loops
When using long control cables, 50/60 Hz ground loops can occur, disturbing the entire
system. Connecting 1 end of the shield with a 100 nF capacitor and keeping the lead short
resolves this issue.
Serial communication control cables
Low-frequency noise currents between drives can be eliminated by connecting 1 end of
the shielded cable to drive terminal 61. This terminal connects to ground through an
internal RC link. Reduce the differential mode interference between conductors by using
twisted-pair cables.
Danfoss A/S © 02/2019 All rights reserved.
4 4
41