14
3.2.2. Screening and earthing
In order to avoid radio interference, care must be taken with the design and
connection of digital drives to avoid EMC disturbances during operation.
Digital drives are not more vulnerable to interference than analog drives, but the
effect is generally different. Interference of analog devices becomes obvious as
irregularities in speed. Interference of digital drives may cause
program errors; therefore it is important that the drives are inhibited
immediately when interference occurs. This is done by setting the
TRIP function (CCr).
In order to avoid these problems, care must be taken with ground
(GND), protective earth (PE) connections as well as screening.
•
Screen control cables and motor cables.
•
Ensure effective screening:
−
a non-earthed conductior should be used to maintain screen
integrity where cahbles are interrupted (terminal strips,
relays, fuses).
Caution!
To increase the EMC (electromagnetic compatibility), the reference GND is
connected to the protective earth (PE) inside the drive.
To ensure an optimum interference suppression, the screening and the GND-PE-
connection is made differently for single drive and multi drive
networks.
Single drive
•
Connect the screen of the control cables to PE of the drive at
one end to avoid earth loops.
•
GND and PE are connected by a jumper inside the drive.
•
In case of firmly installed computer connections, a mains
isolation (e.g. Lenze Converter 2101) is mandantory between
computer and axis module.
•
The screens of the motor cables
−
should be as large as possible.
−
connected to the two sides.
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