Table of Contents
Advertisement
EMC-correct electrical installation
Following these guidelines is advised, where
compliance with EN 61000-6-3/4, EN 55011 or
EN 61800-3 First environment is required. If the
installation is in EN 61800-3 Second environment,
then it is acceptable to deviate from these guidelines.
It is however not recommended.
Good engineering practice to ensure EMC-correct
electrical installation:
•
Use only braided screened/armoured motor
cables and control cables.
The screen should provide a minimum coverage
of 80%.The screen material must be 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 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 screen/armour/conduit to earth
at both ends for motor cables and control
cables. See also Earthing of braided screened/
armoured control cables.
•
Avoid terminating the screen/armour with twisted
ends (pigtails). Such a termination increases the
high frequency impedance of the screen, which
reduces its effectiveness at high frequencies. Use
low impedance cable clamps or glands instead.
•
Ensure good electrical contact between the
mounting plate and the metal chassis of
the frequency converter.
•
Use starwashers and galvanically conductive
installation plates to secure good electrical
connections for IP 20 installations.
•
Avoid using unscreened/unarmoured motor
or control cables inside cabinets housing the
drive(s), where possible.
The illustration shows an example of an EMC-correct
electrical installation of an IP 20 frequency converter.
The frequency converter has been fitted in an
installation cabinet with an output contactor and
connected to a PLC, which in this example is installed
in a separate cabinet. Other ways of making the
installation may have as good an EMC performance,
provided the above guide- lines to engineering practice
are followed. Please note that when unscreened
cables and control wires are used, some emission
MG.70.A1.02 - VLT is a registered Danfoss trademark
VLT® 7000 Booster
requirements are not complied with, although the
immunity requirements are fulfilled.
See the section EMC test results for further details.
29
Advertisement
Table of Contents
