Motor Thermal Protection - Danfoss VLT AQUA Drive FC 202 Operating Instructions Manual

How to Install
NOTICE
Installations with cables connected in a common joint as
in Illustration 4.31, are only recommended for short cable
lengths.
NOTICE
When motors are connected in parallel, 1-29 Automatic
Motor Adaptation (AMA) cannot be used.
4 4
NOTICE
The electronic thermal relay (ETR) of the frequency
converter cannot be used as motor overload protection
for the individual motor in systems with parallel-
connected motors. Provide further motor overload
protection, for example thermistors in each motor or
individual thermal relays (circuit breakers are not
suitable as protection).
Illustration 4.31 Parallel Motor Connection
Problems may arise at start-up 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-up and at low RPM values.
50
Operating Instructions
LC lter
Danfoss A/S © Rev. 06/2014 All rights reserved.

4.5.3 Motor Thermal Protection

The electronic thermal relay in the frequency converter has
received UL-approval for single motor overload protection,
when 1-90 Motor Thermal Protection is set for [4] ETR Trip
and 1-24 Motor Current are set to the rated motor current
(see motor nameplate).
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. When 1-90 Motor Thermal
Protection is set to [20] ATEX ETR and is combined with the
use of MCB 112, it is possible to control an Ex-e motor in
explosion hazardous areas. Consult the product relevant
Programming Guide for details on how to set up the
frequency converter for safe operation of Ex-e motors.
MG20Y202