Parallel Connection Of Motors - Danfoss VLT FC51 Design Manual

How to Install ®
VLT Micro Drive FC 51 Design Guide

6.17 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 for
INV
the frequency converter.
When motors are connected in parallel, 1-29 Automatic
Motor Tuning (AMT) cannot be used.
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.
6 6
The electronic thermal relay (ETR) of the frequency
converter cannot be used as motor protection for the
individual motor of systems with parallel-connected
motors. Provide further motor protection by for example
thermistors in each motor or individual thermal relays.
LC filter
(Circuit breakers are not suitable as protection).
Illustration 6.18 Parallel Connection of Motors
MG02K302 - Rev. 2013-12-03 55