Installation
01/02 AWB8230-1413GB
24
Fit additional RFI filters or mains filters and frequency inverters as
closely as possible to each other and on a single metal mounting
plate.
Lay cables in the control cabinet as near as possible to the earth
potential. Cables that hang freely act as antennae.
To prevent transfer of electromagnetic energy, lay interference-
suppressed cables (e.g. the mains supply line before the filter) and
signal lines as far away as possible (at least 10 cm) from
HFconducting cables (e.g. mains supply cable after a filter, motor
power cable). This applies especially where cables are routed in
parallel. Never use the same cable duct for interference-
suppressed and HF cables. Where crossovers are unavoidable,
cables should always cross at right angles to each other.
Never lay control or signal cables in the same duct as power
cables. Analog signal cables (for measured values, setpoints and
correction values) must be screened.
Earthing
Connect the base plate (mounting plate) with the protective earth
using a short cable. Lay all conducting components (frequency
inverter, mains filter, motor filter, mains choke) with an HF wire,
and the protective conductor in a star configuration from a central
earthing point. This achieves the best results.
Make sure that the earthing measures have been correctly
implemented (
a
fig. 14). No other device which has to be
earthed should be connected to the earthing terminal of the
frequency inverter. If more than one frequency inverter is used, the
earthing cables should not form a closed loop.
Screening
Unscreened cables behave like antennae, i.e. they act as
transmitters and receivers. To ensure EMC-compliant connection,
screen all interference-emitting cables (frequency inverter/motor
output) and interference-sensitive cables (analog setpoint and
measured value cables).
The effectiveness of the cable screen depends on a good screen
connection and a low screen impedance. Use only screens with
tinned or nickel-plated copper braiding, braided steel screens are
unsuitable. The screen braid must have an overlap ratio of at least
85 percent and an overlap angle of 90°.
Figure 14:
Star-type point-to-point earthing
e
PE
Z1
G1
Gn
Zn
PE
PE
M1
PE
PE
M
3
h
Mn
M
3
h
Figure 15:
Sample motor cable
a
Copper screen braid
b
PVC outer sheath
c
Drain wire (copper)
d
PVC core insulation
3
x
black, 1
x
green/yellow
e
Textile braid and PVC inner
b
a
e
d
c
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