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8–8
8.4
Electromagnetic compatibility
8.4.1
General
8.4.2
Interference
8.4.3
Signal-to-interference ratio
The electromagnetic compatibility (EMC) is the capability of an electrical unit
to operate satisfactorily in its electromagnetic environment without
influencing this environment, to which other units belong, to more than a
permitted degree (EN 61 000-4-1).
An important aim in automation technology is to achieve the greatest
possible level of system availability. For this reason, there is a strong interest
in avoiding standstill times due to interference.
Possible sources of interference for the user are:
D internally generated interference, e.g. by frequency converter, inductive
loads etc.
D externally generated interference, e. g. lightning discharge, mains fluc-
tuations etc.
These sources of interference affect the device, the interference trough, in
different ways. The main interaction paths of the interference are:
D emitted interference interaction
D conducted interference interaction
D electrostatic discharges
Conducted interference can change into emitted interference and vice
versa. For example, the conducted interference on a cable causes a field
which emits onto a cable fitted in parallel and also causes conducted
interference.
The signal-to-interference ratio is the ability of a device or component to
tolerate interference up to a certain level without restriction. Electronic units
such as control units have a significantly lower signal-to-interference ratio
than other electrical equipment, e. g. contactors.
1070 072 302-101 (01.06) GB
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