S5-115F Manual
Installation Guidelines
3.5
Installing Programmable Controllers in Conformity with EMC Guidelines
Measures to suppress interference are frequently only taken when the controller is already in
operation and reception of a signal has already been affected. In most cases, such interference is
attributable to inadequate reference potentials caused by faulty installation of the programmable
controller.
When installing the programmable controller, you must ensure that all inactive metal parts have
surface contact grounding. Correct grounding creates a uniform reference potential for the
controller and reduces the effects of strays.
Grounding means the conductive connection of all inactive metal parts. The total of all
interconnected inactive parts is called the ground.
Inactive metal parts are all conductive parts that have at least basic electrical isolation from active
parts and that are energized only in case of a fault.
Even in case of a fault, the ground must
not carry a dangerous touch voltage. The ground must
therefore be connected with the protective conductor. To avoid ground loops, you must always
connect locally separated ground configurations (cubicles, structural parts and machine parts) to
the protective conductor system in a star configuration.
Note the following when grounding:
•
Connect the inactive metal parts as carefully as the active parts.
•
Make sure that the metal-to-metal connections are of low impedance, e.g. through large-
surface contacting with good conductivity.
•
If you include enamelled or anodized metal parts in the grounding, these insulating protective
layers must be penetrated. For this purpose, use special contact washers or remove the
insulation layers.
•
Protect joints against corrosion, for example, by means of grease.
•
Movable ground parts (e.g. cubicle doors) must be connected via flexible grounding strips. The
grounding strips should be short and have a large surface, since the surface is decisive for the
discharge of high-frequency interference.
EWA 4NEB 811 6148-02
3-41
