ABB ACS880 - Page 73

messages over an electrical cable or fiber optic link. The master can read feedback
signals from up to 3 selected followers.
M
~
M
~
Speed-controlled master
Torque-or-speed
controlled follower
Process master
Process
follower
Master
DDCS
(For example)
Control word
Speed reference
Torque reference
Master/follower link
(For example)
Status word
01.01, 01.10
Fieldbus control
External control system
(e.g. PLC)
DDCS
Follower
The master drive is typically speed-controlled and the other drives follow its torque
or speed reference. In general, a follower should be
• torque-controlled when the motor shafts of the master and the follower are
rigidly coupled by gearing, chain etc. so that no speed difference between the
drives is possible.
• speed-controlled when the motor shafts of the master and the follower are
flexibly coupled so that a slight speed difference is possible. When both the
master and the follower are speed-controlled, drooping is also typically used
(see parameter 25.8). The distribution of load between the master and follower
can alternatively be adjusted as described under Load share function with a
speed-controlled follower below.
Program features 73