VLT
®
8000 AQUA
Problems may arise at the start and at low rpm values if
the motor sizes are widely different. This is because the
relatively high ohmic resistance in small motors calls for
a higher voltage at the start and at low rpm values.
In systems with motors connected in parallel, the
electronic thermal relay (ETR) of the frequency
converter cannot be used as motor protection for
the individual motor. Consequently, additional motor
protection is required, such as thermistors in earth
motor (or individual thermal relays).
NB!:
Parameter 107
Automatic Motor Adaptation,
AMA
and
Automatic Energy Optimization, AEO
in parameter 101
Torque characteristics
cannot
be used motors are connected in parallel.
■
Motor cables
See
Technical data
for correct sizing of motor
cable cross-section and length.
Always comply with national and local regulations
on cable cross-sections.
NB!:
If an unscreened cable is used, some
EMC requirements are not complied with,
see
EMC test results
.
If the EMC specifications regarding emission are
to be complied with, the motor cable must be
screened, unless otherwise stated for the RFI filter
in question. It is important to keep the motor cable
as short as possible so as to reduce the noise level
and leakage currents to a minimum.
The motor cable screen must be connected to the
metal cabinet of the frequency converter and to the
metal cabinet of the motor. The screen connections
are to be made with the biggest possible surface (cable
clamp). This is enabled by different installation devices
in the different frequency converters. Mounting with
twisted screen ends (pigtails) is to be avoided, since
these spoil the screening effect at higher frequencies.
If it is necessary to break the screen to install a motor
isolator or motor contactor, the screen must be
continued at the lowest possible HF impedance.
■
Motor thermal protection
The electronic thermal relay in UL-approved frequency
converter has received UL-approval for single motor
protection, as long as parameter 117
Motor thermal
protection
has been set to ETR Trip and parameter 105
Motor current, I
VLT,N
has been programmed for the rated
motor current (can be read from the motor nameplate).
■
Earth connection
Since the leakage currents to earth may be higher
than 3.5 mA, the frequency converter must always
be earthed in accordance with applicable national
and local regulations. In order to ensure good
mechanical connection of the earth cable, its cable
cross-section must be at least 8 AWG/10mm
2
. For
added security, an RCD (Residual Current Device)
may be installed. This ensures that the frequency
converter will cut out if the leakage currents get too
high. See RCD Instructions MI.66.AX.02.
■
Installation of 24 Volt external DC supply
Torque: 0.5 - 0.6 Nm
Screw size:
M3
No.
Function
35(-), 36 (+)
24 V External DC supply
(Available with VLT 8016-8652 380-480 V and VLT 8052-8652
525-690 V only)
24 V external DC supply can be used as low-voltage
supply to the control card and any option cards
installed. This enables full operation of the LCP (incl.
parameter setting) without connection to mains.
Please note that a warning of low voltage will be
given when 24 V DC has been connected; however,
there will be no tripping. If 24 V external DC supply
is connected or switched on at the same time as the
mains supply, a time of min. 200 msec. must be set
in parameter 111,
Start delay
. A pre-fuse of min. 6
Amp, slow-blow, can be fitted to protect the external
24 V DC supply. The power consumption is 15-50
W, depending on the load on the control card.
NB!:
Use 24 V DC supply of type PELV to ensure
correct galvanic isolation (type PELV) on the
control terminals of the frequency converter.
MG.83.A2.02 - VLT is a registered Danfoss trademark
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