Motion Coordinator Technical Reference Manual
Installation 3-9
EMC Considerations
EMC Considerations
Most pieces of electrical equipment will emit noise either by radiated emissions
or conducted emissions along the connecting wires. This noise can cause interfer-
ence with other equipment near by which could lead to that equipment malfunc-
tioning. These sort of problems can usually be avoided by careful wiring and
following a few basic rules.
1) Mount noise generators such as contactors, solenoid coils and relays as far away
as possible from the modules.
2) Where possible use solid-state contactors and relays.
3) Fit suppressors across coils and contacts.
4) Route heavy current power and motor cables away from signal and data cables.
5) Ensure all the modules have a secure earth connection.
6) Where screened cables are used terminate the screen with a 360 degree termina-
tion, if possible, rather than a “pig-tail” and connect both ends of the screen to
ground.
The screening should be continuous, even where the cable passes through a cabi-
net wall or connector.
These are just very general guidelines and for more specific advice on specific
controllers, see the installation requirements later in this chapter. The consider-
ation of EMC implications is now more important than ever since the introduction
of the EC EMC directive which makes it a legal requirement for the supplier of a
product to the end customer to ensure that it does not cause interference with
other equipment and that it is not itself susceptible to interference from other
equipment.
Background to EMC Directive
Since 1st January 1996 all suppliers of electrical equipment to end users must
ensure that their product complies with the 89/336/EEC Electromagnetic Com-
patibility directive. The essential protection requirements of this directive are:
1) Equipment must be constructed to ensure that any electromagnetic disturbance
it generates allows radio and telecommunications equipment and other apparatus
to function as intended.
2) Equipment must be constructed with an inherent level of immunity to externally
generated electromagnetic disturbances.
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