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8.9 EMC-correct Installation
8.9.1 Electrical Installation - EMC Precautions
The following is a guideline for good engineering practice when installing adjustable frequency drives. Follow these guidelines to comply with EN 61800-3
First environment
. If the installation is in EN 61800-3
Second environment,
i.e., industrial networks, or in an installation with its own transformer, deviation
from these guidelines is allowed but not recommended. See also paragraphs
CE Labeling,
General Aspects of EMC Emission
and
EMC Test Results
.
Good engineering practice to ensure EMC-correct electrical installation:
•
Use only braided shielded/armored motor cables and braided shielded/armored control cables. The shield should provide 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 line cable.
•
Installations using rigid metal conduits are not required to contain shielded cable, but the motor cable must be installed in conduit separate from
the control and line cables. Full connection of the conduit from the drive to the motor is required. The EMC performance of flexible conduits
varies greatly, and information from the manufacturer must therefore be obtained.
•
Connect the shield/armor/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 shield at both ends. If so, connect the shield at the adjustable frequency drive. See also
Grounding of Braided Shielded/Armored
Control Cables
.
•
Avoid terminating the shield/armor with twisted ends (pigtails). It increases the high frequency impedance of the shield, which reduces its
effectiveness at high frequencies. Use low impedance cable clamps or EMC cable connectors instead.
•
Avoid using unshielded/unarmored motor or control cables inside cabinets housing the drive(s), whenever this can be avoided.
Leave the shield as close to the connectors as possible.
The illustration shows an example of an EMC-correct electrical installation of an IP 20 adjustable frequency drive. The adjustable frequency drive 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 performing the installation
may result in an equally effective EMC performance, provided the above guidelines for engineering practice are followed.
If the installation is not carried out according to the guidelines, and if non-shielded cables and control wires are used, some emission requirements will
not be fulfilled, although the immunity requirements will be. See the paragraph
EMC test results
.
FC 300 Design Guide
8 Electrical Installation
MG.33.BC.22 - VLT
®
is a registered Danfoss trademark
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