Trane TR170 - Grounding Shielded Cables

2.7 Grounding Shielded Cables
Connect the shielded control cables to the metal cabinet
of the frequency converter with cable camps at both ends.
Illustration 2.3 shows ground cabling for optimal results.
Correct grounding
To ensure the best possible electrical connection, t
control cables and cables for serial communication with
cable clamps at both ends.
Illustration 2.2 Correct Grounding
Incorrect grounding
Do not use twisted cable ends (pigtails) since they increase
shield impedance at high frequencies.
Ground potential protection
When the ground potential between the frequency
converter and the PLC or other interface device is dierent,
electrical noise may occur that can disturb the entire
system. Resolve the electrical noise by
tting
an equalizing
cable next to the control cable. Minimum cable cross-
section is 10 mm
2
(8 AWG).
1
Minimum 10 mm
2
(8 AWG)
2 Equalizing cable
Illustration 2.3 Ground Potential Protection
50/60 Hz ground loops
When using long control cables, 50/60 Hz ground loops
may occur that can disturb the entire system. Resolve the
ground loops by connecting 1 end of the shield with a
100 nF capacitor and keeping the lead short.
Illustration 2.4 50/60 Hz Ground Loops
Serial communication control cables
Low-frequency noise currents between frequency
converters can be eliminated by connecting 1 end of the
shielded cable to frequency converter terminal 61. This
terminal connects to ground through an internal RC link.
To reduce the dierential mode interference between
conductors, use twisted-pair cables.
Illustration 2.5 Serial Communication Control Cables
Frequency Converter Control
22 02/2017 All rights reserved. BAS-SVM04B-EN
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