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.
Note: With a speed-controlled follower (without load sharing), pay attention to
the acceleration and deceleration ramp times of the follower. If the ramp times
are set longer than in the master, the follower will follow its own
acceleration/deceleration ramp times rather than those from the master. In general,
it is recommended to set identical ramp times in both the master and the
follower(s). Any ramp shape settings (see parameters 23.16…23.19) should only
be applied in the master.
Program features 67
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