Additional Connections; Motor Thermal Protection - Danfoss VLT AQUA High Power Operating Instructions Manual

VLT AQUA High Power Operation Instructions

3.10. Additional Connections

3.10.1. Parallel Connection of Motors
The frequency converter can control several
parallel-connected motors. The total current
consumption of the motors must not exceed
the rated output current I
converter.
Problems may arise at start and at low RPM values if motor sizes are widely different because
small motors' relatively high ohmic resistance in the stator calls for a higher voltage at start and
at low RPM values.

3.10.2. Motor Thermal Protection

The electronic thermal relay in the frequency converter has received the UL-approval for single
motor protection, when par. 1-90
current, I
For thermal motor protection it is also possible to use the MCB 112 PTC Thermistor Card option.
This card provides ATEX certificate to protect motors in explosion hazardous areas, Zone 1/21 and
Zone 2/22. Please refer to the
for the frequency
M,N
NB!
Installations with cables con-
nected in a common joint as in
the illustration below, is only
recommended for short cable
lengths.
NB!
When motors are connected in
Automatic
parallel, par. 1-29
Motor Adaptation (AMA)
be used.
NB!
The electronic thermal relay
(ETR) of the frequency convert-
er cannot be used as motor pro-
tection for the individual motor
of systems with parallel-connec-
ted motors. Provide further mo-
tor protection by e.g. thermis-
tors in each motor or individual
thermal relays (circuit breakers
are not suitable as protection).
Motor Thermal Protection
is set to the rated motor current (see motor name plate).
M,N
Design Guide
®
MG.20.P1.02 - VLT is a registered Danfoss trademark
cannot
is set for
for further information.
3. How to Install
ETR Trip and par. 1-24 Motor
3
67