VLT
®
6000 HVAC
Installation
■
Direction of motor rotation
The factory setting is for clockwise rotation with the
frequency transformer output connected as follows.
Terminal 96 connected to U-phase
Terminal 97 connected to V-phase
Terminal 98 connected to W-phase
The direction of motor rotation can be changed by
switching two phases in the motor cable.
■
Parallel coupling of motors
VLT 6000 HVAC is able to control several motors
connected in parallel. If the motors are to have
different rpm values, the motors must have
different rated rpm values. Motor rpm is changed
simultaneously, which means that the ratio between
the rated rpm values is maintained across the range.
The total current consumption of the motors is
not to exceed the maximum rated output current
I
VLT,N
for the frequency converter.
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 each
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 if 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.
MG.60.C7.02 - VLT is a registered Danfoss trademark
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