Brochure/Catalogue

Electromagnetic compatibility
Electromagnetic compatibility
EMC – electromagnetic compatibility – means
the trouble-free interaction between electrical and electronic
systems and devices without mutual interference. In this
respect, any electrical item can act both as transmitter
(source of interference) and receiver (potentially susceptible
device) simultaneously.
Normally it is not sufcient to construct an EMC-compliant
electrical or electronic system using EMC-compliant
components and to then expect that everything will operate
smoothly. Only when you use the proper surge protection
devices in the proper places in the facility, can you operate
without outages using coupled surge voltages. The method
for using surge protection devices is also linked to the
inuence of interference sinks and interference sources.
It integrates with the lightning protection zone strategy
and insulation coordination to form a complete protection
system.
EMC laws and directives
There are a multitude of standards and statutory
requirements aimed at controlling mutual interference-free
operation. With the establishment of the unied European
market in 1989, the EEC Directive (EN 50-370 part 1+2)
on electromagnetic compatibility was adopted and then
implemented into national law. In Germany, the law on the
electromagnetic compatibility (EMVG) was endorsed in
1992. The current version of this law was passed in 2008 as
was the international standard IEC 61000. Electromagnetic
inuences can be caused by natural processes, e.g. a
lightning strike, and also technical processes, e.g. high-speed
changes in the status of currents and voltages.
We distinguish between periodic interference (system hum,
RF irradiation), transient interference (brief, often high-energy
pulses) and noise (broad distribution of interference energy
across the frequency range).
The model used in EMC observations designates the
transmitter as the source of interference emission and
the receiver as the interference drain. The transmission
of the interference takes place via line-bound and/or eld-
bound (H-eld/E-eld) coupling mechanisms.
When considered as a source of interference, a device or a
system may not exceed emissions thresholds specied in the
EMC standards.
When considered as a potentially susceptible device, the
same system must exhibit the immunity to interference
specied in the standards.
However, the arrangement of various electrical systems
within a complex plant or in a room and the many lines for
power supplies, inputs and outputs to controls and bus
systems give rise to diverse potential inuences. Surges can
be introduced by lightning, switching operations, etc. via the
various coupling paths. This can lead to the following effects:
• Reduced functionality
• Malfunctions
• Failure of functions
• Damage
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The basics of lightning and surge protection
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