Appendix: Important notes for crane operators and crane operating companies
© 2009 Hirschmann Automation and Control GmbH · Branch Office Ettlingen · eMail: [email protected] · www.hirschmann.com
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24 183 19 1012e (Generic) / 2009-02-26 / Rev. 01 / rk.
NOTICE 4
Notes on the electromagnetic compatibility (EMC) of electronic
systems under the effect of electromagnetic fields
Electromagnetic fields increasingly affect electronic systems and can cause malfunctions; they can be avoided
by taking preventive state-of-the-art measures:
1. Preventive measures are based primarily on the fundamental principle of screening electronic circuits
against radiating high frequency by a closed low-ohm protective skin for high-frequency interference.
−
All components have outer housings made of metal with earthing option;
−
Only cables with shielding braid are used. The shielding layer must be made so that it is readily
conductive over the surface at all connections.
−
Connecting the crane earth and the electronic earth at only one point in the system.
2.
The general measures listed in item 1 cannot however ensure complete protection against electromagnetic
fields in the individual case as the scale and type of effect depends on the local conditions.
The influencing factors include:
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particularly unfavourable arrangement of antennas to the system,
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very high transmission performance,
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consistent compliance with the measures in item 1 not possible due to local conditions,
−
long
cables,
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coupling of interference in the power lines.
In unfavourable situations, therefore, it is essential to take measures over and above preventive
precautions, in compliance with the principles stated in item 1, experimentally on site, e.g.:
•
insertion of filters or short-circuiting of interference frequencies by condensors,
•
making or breaking earth connections,
•
use of double-screened cables (guarded shield system).