Parallel Connection Of Motors; Motor Thermal Protection - Danfoss VLT AQUA Drive FC 202 Operating Instructions Manual

Electrical Installation
•
The brake engages when the output frequency is
less than the frequency set in 2-21 Activate Brake
Speed [RPM] or 2-22 Activate Brake Speed [Hz], only
if the frequency converter completes a stop
command.
If the frequency converter is in alarm mode or in an
overvoltage situation, the mechanical brake immediately
cuts in.
4 4

4.9.2 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
the frequency converter.
NOTICE
Installations with cables connected in a common joint as
in Illustration 4.17, is only recommended for short cable
lengths.
NOTICE
When motors are connected in parallel, 1-29 Automatic
Motor Adaptation (AMA) cannot be used.
NOTICE
The electronic thermal relay (ETR) of the frequency
converter cannot be used as motor protection for the
individual motor in systems with parallel-connected
motors. Provide further motor protection with
thermistors in each motor or individual thermal relays.
Circuit breakers are not suitable as protection.
40
Operating Instructions
for
M,N
Problems are possible at start and at low RPM values if
motor sizes vary widely. The relatively high ohmic
resistance in the stator of small motors calls for a higher
voltage at start and at low RPM values.

4.9.3 Motor Thermal Protection

The electronic thermal relay in the frequency converter has
received UL-approval for single motor protection, when
1-90 Motor Thermal Protection is set for [4] ETR Trip 1 and
1-24 Motor Current is set to the rated motor current (see
motor name plate).
For thermal motor protection, it is also possible to use the
VLT
ATEX certification to protect motors in explosion hazardous
areas, Zone 1/21 and Zone 2/22. When 1-90 Motor Thermal
Protection is set to [20] ATEX ETR and MCB 112 are
combined, it is possible to control an Ex-e motor in
explosion hazardous areas. Consult the Programming Guide
for details on how to set up the frequency converter for
safe operation of Ex-e motors.
Danfoss A/S © Rev. 2014-01-22 All rights reserved.
LC lter
Illustration 4.17 Installations with Cables Connected in a
Common Joint
®
PTC Thermistor Card MCB 112. This card provides
MG21B202