5.6 Safety
5.6.1 High Voltage Test
Carry out a high voltage test by short-circuiting terminals
U, V, W, L
1
, L
2
and L
3
. Energize maximum 2.15 kV DC for
380–500V adjustable frequency drives and 2.525 kV DC for
525–690 V adjustable frequency drives for one second
between this short-circuit and the chassis.
WARNING
When running high voltage tests of the entire installation,
interrupt line power and the motor connection if the
leakage currents are too high.
5.6.2 Safety Ground Connection
The Adjustable frequency drive has a high leakage current
and must be grounded appropriately for safety reasons
according to EN 50178.
WARNING
The ground leakage current from the Adjustable frequency
drive exceeds 3.5 mA. To ensure a good mechanical
connection from the ground cable to the ground
connection (terminal 95), the cable cross-section must be
at least 0.016 in
2
[10 mm
2
] or two rated ground wires
terminated separately.
5.7 EMC-correct Installation
5.7.1 Electrical Installation - EMC
Precautions
The following is a guideline for good engineering practice
when installing adjustable frequency drives. 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 labeling
,
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 shielded/armored motor cables
and braided shielded/armored control cables. The
shield should provide 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 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/armor/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
5.7.3 Grounding of Shielded/Armored Control
Cables
.
•
Avoid terminating the shield/armor 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/unarmored motor or
control cables inside cabinets housing the
drive(s), whenever this can be avoided.
Leave the shield as close to the connectors as possible.
Figure 5.36
shows an example of an EMC-compliant
electrical installation of an IP20 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
performing the installation may result in an equally
effective EMC performance, provided the above guidelines
for 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
2.9.3 EMC
Test Results (Emission)
.
How to Install
VLT
®
HVAC Drive Design Guide
5-34
MG11BB22 - VLT
®
is a registered Danfoss trademark
5
5
