ABB AC 900F, Mounting And Installation Instructions Manual, Page: 84 / 156

Controller earthing Section 6 Wiring
84 M&I – AC 900F Controller
• Keep all connecting lines as short as possible. This is particularly important for
the earthing conductors.
• Make sure to select sufficiently dimensioned wire cross-sections. This is
particularly important for earthing conductors.
• To achieve low-impedance, i.e. optimum contacts over a large surface, proceed
as follows:
– establish vibration-resistant connections,
– use bare contact areas (remove paint, clean surface),
– avoid the use of aluminum parts (oxidize easily),
– select solid plug and screw connections,
– directly earth the cable shields with clips to a well-grounded metallic
surface,
– do not use drain wires (pig-tails),
– do not use toothed washers to lock the screw unions.
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Controller earthing
Proper earthing of the controller requires an earthed mounting plate or metal frame.
Additional earthing measures are only required if the mounting surface or frame
material cannot be earthed. In this case, a short earthing conductor must be
connected to the lower left/right fastening screw of the CPU module. l
The controller is earthed through the DIN rail or both lower fastening screws. Use
yellow chromated steel DIN rails to ensure proper earthing.