VLT
®
FCD Series
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General information about electrical installation
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High voltage warning
The voltage of the frequency converter
is dangerous whenever the equipment is
connected to mains.Incorrect fitting of the
motor or frequency converter may cause damage to
the equipment, serious injury or death. Conse-
quently, the instructions in this manual, as well as
national and local rules and safety regulations must
be complied with.
Touching the electrical parts may be fatal
- even after the equipment has been disconnected
from mains: Wait at least 4 minutes.
NB!:
It is the user’s or fitter’s responsibility to
ensure correct earthing and protection in ac-
cordance with national and local standards.
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Earthing
The following basic points must be considered at in-
stallation:
• Safety earthing: Please note that the frequency
converter has a high leakage current and must
be earthed appropriately for safety reasons. Ap-
ply local safety regulations.
• High frequency earthing: Keep earthing cables as
short as possible.
Connect the different earthing systems, thereby en-
suring the lowest possible conductor impedance.
The lowest possible conductor impedance is
achieved by keeping the conductor as short as pos-
sible and by using the greatest possible surface
area. A flat conductor, for example, has a lower HF-
impedance than a round conductor, calculated for
the same conductor cross-section C
VESS
. If several
units are installed on a common metal structure, it
should be used as a joint earth reference plate. The
metal cabinets of the different units must be fitted to
the metal structure at the lowest possible HF-
impedance. With this feature, different HF-voltages
will not arise in different units, and there will be no
noise currents in cables used to connect units.
Noise radiation will be reduced. In order to achieve
a low HF-impedance, the fastening bolts of the units
can be used as HF-connection to the metal struc-
ture. It is necessary to remove any layers of isolating
paint or similar from the attachment points.
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Cables
The control cable and the mains cable should be in-
stalled separately from motor cables to prevent noise
transfer. As a rule a distance of 20 cm is sufficient,
but it is recommended that the distance is as great
as possible, particularly when cables are installed in
parallel over large distances.
For sensitive signal cables such as telephone or
data cables the greatest possible distance is recom-
mended. Please note that the required distance
depends on the installation and the sensitivity of the
signal cables, and that for this reason exact values
cannot be given.
When being placed in cable trenches, sensitive ca-
bles may not be placed in the same cable trench as
the motor cable. If signal cables run across power
cables, this is done at an angle of 90 degrees. Re-
member that all noise-filled inlet and outlet cables to
a cabinet must be screened/armoured.
See also
EMC-compliant electrical installation
.
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Screened/armoured cables
The screen must have low HF impedance, which is
achieved by a braided screen of copper, aluminium
or iron. Screen reinforcement intended for mechani-
cal protection, for example, is not suitable for
EMC-correct installation.
See also
Use of EMC-correct cables
.
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Extra protection
ELCB relays, multiple protective earthing or earthing
can be used as extra protection, provided that local
safety regulations are complied with. In the case of
an earth fault, a DC content may develop in the
faulty current. Never use an RCD (ELCB relay), type
A, as it is not suitable for DC faulty currents. If ELCB
relays are used, local regulations must be complied
with.
If ELCB relays are used, they must be:
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Suitable for protecting equipment with a DC con-
tent in the faulty current (3-phase bridge rectifier)
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Suitable for a pulse-shaped, brief discharge on
power-up
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Suitable for a high leakage current.
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High voltage test
A high voltage test can be performed by short-
circuiting terminals U, V, W, L1, L2 and L3, and
MG.04.A1.02 - VLT is a registered Danfoss trade mark
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