09/01 AWB8230-1412GB
EMC compliance
25
The screened cable between frequency inverter and motor should
be as short as possible. Connect the screen to earth at both ends
of the cable using a large contact surface connection.
Lay the cables for the supply voltage separately from the signal
cables and control cables.
Never unravel the screening or use pigtails to make a connection.
If contactors, maintenance switches, motor protection relays,
motor reactors, filters or terminals are installed in the motor
cabling, interrupt the screen near these components and connect
it to the mounting plate (PES) using a large contact surface
connection. The free, unscreened connecting cables should not be
longer then about 100 mm.
Example: Maintenance switch
In an EMC-compliant control cabinet (metal-enclosed, damped to
about 10 dB), the motor cables do not need to be screened
provided that the frequency inverter and motor cables are spatially
separated from each other and arranged in a separate partition
from the other control system components. The motor cable scree-
ning must then be connected via a large surface area connection
at the control cabinet (PES).
The control cable and signal (analog setpoint and measured value)
cable screens must be connected only at one cable end. Connect
the screen to ground using a large-area contact surface; ensure
that the connection has a low impedance. Digital signal cable
screens must be connected at both cable ends with large-surface,
low-resistance connections.
Figure 16: Inadmissible screen grounding (pigtails)
Figure 17: Maintenance switch, e.g. T… in an enclosure
a Metal plate
b Insulated PE-terminal
PES
PES
a
b
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