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 con-
nected 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 con-
sumption 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 pro-
tection is required, such as thermistors in each motor
(or individual thermal relays).
NB!
Parameter 107
Automatic Motor Adapta-
tion
, AMA and
Automatic Energy Optimi-
zation
, AEO in parameter 101
Torque
characteristic
s 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, un-
less 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 differentT 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 con-
tinued at the lowest possible HF impedance.
VLT
®
6000 HVAC Series
86
MG.61.B5.02 - VLT
®
is a registered Danfoss trademark