5.12 EMC Recommendations
The following is a guideline to good engineering practice
when installing frequency converters. Follow these
guidelines in compliance with EN/IEC 61800-3 First
environment. If the installation is in EN/IEC 61800-3 Second
environment, industrial networks, or in an installation with
its own transformer, deviation from these guidelines is
allowed but not recommended.
Good engineering practice to ensure EMC-correct
electrical installation:
•
Use only braided shielded/armored motor cables
and braided shielded control cables. The shield
provides a minimum coverage of 80%. The shield
material must be metal, not limited to but
typically copper, aluminum, steel, or lead. There
are no special requirements for the mains cable.
•
Installations using rigid metal conduits are not
required to use shielded 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
exible conduits varies a lot and information from
the manufacturer must be obtained.
•
Connect the shield conduit to ground at both
ends for motor cables and for control cables.
Sometimes, it is not possible to connect the
shield in both ends. If so, connect the shield at
the frequency converter. See also
chapter 5.12.2 Grounding of Shielded Control
Cables.
•
Avoid terminating the shield with twisted ends
(pigtails). It increases the high frequency
impedance of the shield, which reduces its
eectiveness at high frequencies. Use low
impedance cable clamps or EMC cable glands
instead.
•
Avoid using unshielded motor or control cables
inside cabinets housing the frequency converter,
whenever possible.
Leave the shield as close to the connectors as possible.
Illustration 5.13 shows an example of an EMC-correct
electrical installation of an IP20 frequency converter. The
frequency converter is tted 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 could have just as good an EMC performance,
provided the guidelines to engineering practice are
followed.
If the installation is not carried out according to the
guideline, and if unshielded cables and control wires are
used, some emission requirements are not in compliance,
although the immunity requirements are
fullled.
Electrical Installation Installation Guide
MG37K302 Danfoss A/S © 08/2017 All rights reserved. 37
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