01.99 11 Maintenance
© Siemens AG 1999 All Rights Reserved 6FC5198-6AA60-0BP1
SINUMERIK 840C, OEM Version for Windows (BA)
11-7
11.4 Practical tips on remedying electromagnetic
compatibility problems
Electromagnetic compatibility (EMC) means the capacity of an electrical unit
to work properly in a given electromagnetic environment without affecting the
environment in a manner which is not acceptable.
Table 11-2 Tips for fault elimination
Faulty behaviour Possible cause Elimination of fault
Flickering screen characters
or display surface
Adjacent unit producing a
magnetic field (e.g. transformer,
electric motor)
Increase distance between CRT and
source fault (>300 mm). In extreme
cases, shield CRT with
MUMETALL.
The information on the CRT
and the background
information have colours
missing over some areas
Magnetic field of an adjacent
permanent magnet
Remove cause of fault and screen
with MUMETALL.
Note: Effect on screen will only
disappear a few days after removal
of the cause.
Sporadic failure • Contactors not connected • Connect contactors (coils)
• Adjacent machines producing
sparks (welding sets)
• Lay cable to the control
differently (increase distance to
cause of fault)
• Radio transmitter, centralized
multi-station control system
• Additional screening
• Cable with wrong screen
connection, cable with wrong
wire combinations or wrong
characteristics
• Use original cable and check
core assignment
• Interruption in cable
screening (e.g. if a cable
distributor is interposed)
• Connection of cable
screening, screening the point of
interruption (e.g. the cable
distributor)
• Bonding conductor laid
wrongly
• Re-lay bonding conductor
• Control dirty • Clean control (and modules) and
ensure that cleaner air is supplied
Permanent axis offset See possible causes as for
’Sporadic failure’.
See elimination of fault as for
’Sporadic failure’. The actual value
cable acts as the fault sink.
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