ABB ACS880 Series, Firmware Manual

Page: 74 / 764

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 (
19.12
or 19.14 ). Another method is to set one external 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 (page 39) .
With torque control, follower parameter 26.15 can be used to scale the 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
140 ) can be saved with the master settings, another with
the follower settings. The suitable settings can then be activated using for example,
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 trim signal based on a torque reference.
The torque reference is selected by parameter
23.42 (by default, reference 2 received
from the master). Load share is adjusted by parameter 26.15 and activated by the
source selected by 23.40 . Parameter 23.41 provides a gain adjustment for the speed
correction. The final correction signal added to the speed reference is shown by
23.39 . See the block diagram on page 749 .
74 Program features