Baumuller BUG 2, Technical Description And Operations Manual

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Installation EMC Information
22
BUG 3/2/20 Basic Feed Unit
5.96064.02
Baumüller Nürnberg GmbH
Screening
•
The screen is effective against magnetic fields if it is connected to frame ground at both ends.
With electrical fields, the screen is effective when it is connected to frame ground at one end.
However, in the case of (electrical or magnetic) fields with high frequencies (depending on the
length of the line), you must always connect the screen at both ends due to the linkage (electro-
magnetic field).
Connecting the screen to frame ground at both ends ensures that the conductor does not leave the
screening "system housing".
•
Frame-grounding of conductor screens on both sides does not entirely rule out the influence of
earth circuits (potential differences on the frame ground system). However, this is very rare if you
carry out the measures described in the previous sections entitled "Cabling" and "Grounding".
You can also make a capacitive RF connection of a screen to frame ground. This prevents low-
frequency interference due to earth circuits.
Screened cables that pass through different EMC areas must not be separated at terminals, since
screen damping would otherwise be considerably reduced. The cables should be routed to the next
module without interruption.
•
Make the screen connection low-impedance and over a wide surface area. Cable tails that are only
three centimetres long (1 cm of wire = 10 nH) reduce the screening effect in the megahertz range
by up to 30 dB!
NOTE
The braided screen must have a coverage of at least 85%.
The following lines have particularly high levels of interference potential:
−
the motor line
−
the line to the external ballast resistors
−
the line between the mains filter and the converter