ABB ACS880 Series Firmware Manual page 34

34 Program features
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
25.08 Drooping
can alternatively be adjusted as described under
speed-controlled follower
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.
In some applications, both speed control and torque control of the follower are
required. In those cases, the operating mode can be switched by parameter
Ext1 control mode
control location to speed control mode, the other to torque control mode. Then, a
digital input of the follower can be used to switch between the control locations. See
chapter Control locations and operating modes
With torque control, follower parameter
incoming torque reference for optimal load sharing between the master and the
follower. Some torque-controlled follower applications, eg. where the torque is very
low, or very low speed operation is required, may require encoder feedback.
If a drive needs to quickly switch between master and follower statuses, one user
parameter set (see page 90) can be saved with the master settings, another with the
follower settings. The suitable settings can then be activated using eg. digital inputs.
Load share function with a speed-controlled follower
Load sharing between the master and a speed-controlled follower can be used in
various applications. The load share function is implemented by fine-tuning the
follower speed reference with an additional term based on a torque reference. The
torque reference is selected by parameter
default, reference 2 received from the master). Load share is adjusted by parameter
26.15 Load share and activated by the source selected by
correction enable. Parameter
adjustment for the speed correction. The final correction term added to the speed
reference is shown by
page 551.
rate). The distribution of load between the master and follower
below.
or 19.14 Ext2 control
23.41 Follower speed correction gain
23.39 Follower speed correction
Load share function with a
mode). Another method is to set one external
(page 19).
26.15 Load share can be used to scale the
23.42 Follower speed corr torq source
out. See the block diagram on
(19.12
23.40 Follower speed
provides a gain
(by