Emc; Emc-Correct Cables - Danfoss VLT Decentral Drive FCD 302 Design Manual

System Integration
120
100
80
60
3 3
40
20
0
0 10
Illustration 3.17 VT Applications - Maximum Load for a Standard
Motor at 40 °C
Item
‒‒‒‒‒‒‒‒
─ ─ ─ ─
Table 3.12 Legend - VT Applications
NOTE
Over-synchronous speed operation will result in decrease
of the available motor torque, inversely proportional to the
increase in speed. This must be considered during the
design phase to avoid over-loading of the motor.

3.4.4 EMC

3.4.4.1 EMC-correct Cables

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 1.4.3 CE Labelling,2.2.1 General
Aspects of EMC Emissions and 2.2.2 EMC Test Results.
Good engineering practice to ensure EMC-correct
electrical installation:
•
Use only braided screened/armoured motor
cables and braided screened/armoured control
40
20 30 40 50 60 70 80
v %
Description
Maximum torque
Typical torque at VT load
MG04H102 - VLT
®
VLT Decentral Drive FCD 302
1)
•
90 100 110
•
•
•
Leave the screen as close to the connectors as possible.
Illustration 3.18 shows an example of an EMC-correct
electrical installation of an IP20 frequency converter. The
frequency converter is 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 guidelines are followed.
If the installation is not carried out according to the
guidelines, and if unscreened cables and control wires are
used, then certain emission requirements will not be
fulfilled, although the immunity requirements are fulfilled.
See the section 2.2.2 EMC Test Results.
®
is a registered Danfoss trademark
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 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.
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.