Danfoss FC 102 Design Manual page 119

Electrical Installation
metal, not limited to, but typically copper,
aluminium, steel or lead. There are no special
requirements for the mains cable.
•
Installations using rigid metal conduits are not
required to use screened cable, but the motor
cable must be installed in conduit separate from
the control and mains cables. Full connection of
the conduit from the frequency converter to the
motor is required. The EMC performance of
flexible conduits varies a lot and information from
the manufacturer must be obtained.
•
Connect the screen/armour/conduit to ground at
both ends for motor cables as well as for control
cables. In some cases, it is not possible to
connect the screen in both ends. If so, connect
the screen at the frequency converter. See also
chapter 6.8.3 Grounding of Screened Control
Cables.
•
Avoid terminating the screen/armour with twisted
ends (pigtails). It increases the high frequency
impedance of the screen, which reduces its
effectiveness at high frequencies. Use low
Mains-supply
L1
L2
L3
PE
Reinforced protective earth
Illustration 6.62 EMC-correct Electrical Installation of a Frequency Converter in Cabinet
MG11BC02
Design Guide
Panel
PLC etc.
PLC
2
Min. 16 mm
Equalizing cable
Control cables
Min. 200mm
between con-
trol cables,
motor cable and
mains cable
Danfoss A/S © Rev. 06/2014 All rights reserved.
impedance cable clamps or EMC cable glands
instead.
•
Avoid using unscreened/unarmoured motor or
control cables inside cabinets housing the
frequency converter(s).
Leave the screen as close to the connectors as possible.
Illustration 6.62 shows an example of an EMC-correct
electrical installation of an IP20 frequency converter. The
frequency converter is fitted in an installation cabinet with
an output contactor and connected to a PLC, which is
installed in a separate cabinet. Other ways of doing the
installation may have just as good an EMC performance,
provided the above guide lines to engineering practice are
followed.
If the installation is not carried out according to the
guideline, and if unscreened cables and control wires are
used, some emission requirements are not complied with,
although the immunity requirements are fulfilled. See
chapter 2.9.2 EMC Test Results.
Output con-
tactor etc.
Earthing rail
Cable insula-
tion stripped
All cable entries in
one side of panel
Motor cable
Motor, 3 phases and
Protective earth
6 6
117