Laying Cables Within Control Cabinets - Control Technology 2500 Series Installation And Operation Manual

Shielding.
In addition, electronic starters should be used if fluorescent lamps are installed within control cabinets.
The following cable laying instructions apply to shielded twisted pair cables. The cable shield is used to
improve the immunity to electromagnetic interference. PROFIBUS cables should be shielded with a
combination of both conductive braid and conductive foil. In the following, "shield" refers to both
types of shields (braid and foil). A foil shield should not be used on its own, because it is very thin
and can easily be damaged. The cable shield must be connected to the functional ground at both ends
of the cable by making a large-area connection to a grounded conductive surface. When laying the
bus cables, particular care should be taken to ensure that the cable shield (braid shield and foil shield, if
available) is connected to the shield grounding clamp over a large area. The two PROFIBUS data lines
are designated A and B. There are no regulations on which cable core color should be connected to
which of the two data terminals on each fieldbus device; the sole requirement is to ensure that the
same core color is connected to the same terminal (A or B) for all stations throughout the entire
system (across all stations and bus segments). If the data transfer cable has data wires with red and
green insulation, then the following assignment should be used:
Data cable wire A - green
Data cable wire B – red
This rule applies to both the incoming and the outgoing data lines.

Laying cables within control cabinets

If a repeater or fieldbus device is installed within a control cabinet, the cable shield of the incoming bus cable
should be electrically connected to a grounding rail as close as possible to the cable leadthrough using
a shield grounding clamp or similar (see Figure 3-1). The cable shield should continue within the
cabinet to the fieldbus device and be connected there in accordance with the manufacturer's instructions. The
following installation guidelines should be observed. Ensure that the case of the device and also the
control cabinet in which the fieldbus device is mounted have the same ground potential by providing
a large-area metallic contact to ground (use e.g. galvanized steel to ensure a good connection).
Grounding rails should not be attached to painted surfaces. If the above measures are observed,
electromagnetic interference is diverted through the cable's shield.
CTI 2500-RBC Installation and Operation Guide V1.6
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