Emc-Correct Installation; Electrical Installation - Emc Precautions - Danfoss VLT HVAC Design Manual

How to Install
WARNING
The earth leakage current from the frequency converter
exceeds 3.5 mA. To ensure a good mechanical connection
from the earth cable to the earth connection (terminal 95),
the cable cross-section must be at least 10 mm
earth wires terminated separately.

5.7 EMC-correct Installation

5.7.1 Electrical Installation - EMC
Precautions
The following is a guideline to good engineering practice
when installing frequency converters. 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 2.2 CE labelling, 2.9.1 General
Aspects of EMC Emissions and 2.9.3 EMC Test Results
(Emission).
Good engineering practice to ensure EMC-correct
electrical installation:
•
Use only braided screened/armoured motor
cables and braided screened/armoured 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
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VLT HVAC Drive Design Guide
2
or 2 rated
Leave the screen as close to the connectors as possible.
Illustration 5.25 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
2.9.3 EMC Test Results (Emission).
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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 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
5.7.3 Earthing of Screened/Armoured 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
impedance cable clamps or EMC cable glands
instead.
•
Avoid using unscreened/unarmoured motor or
control cables inside cabinets housing the
drive(s), whenever this can be avoided.
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