Grounding Shielded Cables - Danfoss VLT FC 100 Service Manual

Operator Interface and Adju...

2.9 Grounding Shielded Cables

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Connect the shielded control cables with cable clamps at both ends to the metal cabinet of the adjustable frequency drive.
Table 2.8 shows ground cabling for optimal results.
Table 2.8 Grounding Shielded Cables
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Service Manual
Correct grounding control cables and cables for serial communication must be fitted with
cable clamps at both ends to ensure the best possible electrical connection.
Incorrect grounding Do not use twisted cable ends (pigtails) since these increase shield
impedance at high frequencies.
Ground potential protection; When the ground potential between the adjustable frequency
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 will resolve this.
Minimum cable cross section is 8 AWG.
50/60 Hz ground loops; When using long control cables, 50/60 Hz ground loops may occur
that can disturb the entire system. Resolve this by connecting one end of the shield with a 100
nF capacitor and keeping the lead short.
Serial communication control cables Low frequency noise currents between adjustable
frequency drives can be eliminated by connecting one end of the shielded cable to adjustable
frequency drive terminal 61. This terminal connects to ground through an internal RC link. Use
twisted-pair cables to reduce the differential mode interference between conductors.
Danfoss A/S © Rev. 2014-02-10 All rights reserved. MG94A222