3.3.12 Electrical Installation - EMC
Protection
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.
Good engineering practice to ensure EMC-correct electrical
installation
•
Use only braided screened/armoured motor
compressor 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
compressor 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 compressor 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 compressor 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
3.3.11 Electrical Installation, 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
compressor or control cables inside cabinets
housing the frequency converter(s), whenever this
can be avoided.
Leave the screen as close to the connectors as possible.
shows an example of an EMC-correct
electrical installation of an IP 20 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
the paragraph.
How to Install
Operating Instructions VLT
®
CDS302 and CDS303
26
MG34M302 - VLT
®
is a registered Danfoss trademark/Commercial Compressor
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