Danfoss VLT AutomationDrive FC 300 Design Manual page 237

Electrical Installation
Good Engineering Practice to Ensure EMC-compatible 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 line cable.
•
Installations using rigid metal conduits are not required to contain shielded cable, but the motor cable must be
installed in a conduit separate from the control and line cables. Full connection of the conduit from the adjustable
frequency drive to the motor is required. The EMC performance of flexible conduits varies a lot and information
from the manufacturer must be obtained.
•
Connect the shield 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 chapter 7.7.2 Grounding.
•
Avoid terminating the shield 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 non-shielded motor or control cables inside cabinets housing the adjustable frequency drive,
whenever possible.
Leave the shield as close to the connectors as possible.
Figure 7.56 shows an example of an EMC-compatible 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 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 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 chapter 3.5.2 EMC Test Results.
Figure 7.56 EMC-compatible Electrical Installation of an Adjustable Frequency Drive in Cabinet
MG34S222
Design Guide
Danfoss A/S © Rev. 2014-02-10 All rights reserved.
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