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S5-95F
Coupling Mechanisms and Typical Interference Sources at a Glance
Coupling Mechanism
•
Direct Coupling
Interference
Direct coupling
path
SIMATIC S5
•
Capacitive Coupling
Interference
Capacitive
coupling path
SIMATIC S5
•
Inductive Coupling
Interference
Signal
SIMATIC S5
•
Radiated Interference
Interference
Radiation
path
SIMATIC S5
EWA 4NEB 812 6210-02
Guidelines for the Planning and Installation of the Product
Table 3-1. Interference Sources and Their Causes
Cause
Direct or metallic coupling always
occurs when two circuits have a
common conductor.
Capacitive or electrical coupling
occurs between conductors which
are at different potentials.
The degree of coupling is
proportional to the voltage variation
as a function of time.
Inductive or magnetic coupling
occurs between two conductor
loops through which current is
flowing. Interference voltages are
induced by the magnetic fluxes
associated with the currents. The
Inductive
degree of coupling is proportional
coupling
to the current variation as a
path
function of time.
There is a radiation path when a
conductor is subjected to an
electromagnetic wave. Impinging of
the wave results in induced
currents and voltages.
Typical Interference Source
•
Switched devices (supply affected by
inverters and external power supply
units)
•
Motors being started
•
Different potentials of component cases
with a common power supply
•
Static discharges
•
Interference pickup via parallel signal
cables
•
Static discharge of the operator
•
Contactors
•
Transformers, motors, electric welders
•
Parallel AC supply cables
•
Cables with switched currents
•
Signal cables with a high frequency
•
Unconnected coils
•
Local transmitters (e.g. two-way radios)
•
Spark gaps (spark plugs, collectors of
electric motors, welders)
3-3
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