General - ABB ACS800 Series Firmware Manual

Master/Follower

General

The Master/Follower function is designed for applications in which the system is run
by several ACS800 drives and the motor shafts are coupled to each other via
gearing, chain, belt etc. Thanks to the Master/Follower function, the load can be
evenly distributed between the drives.
The external control signals are connected to the Master only. The Master controls
the Follower(s) via a fibre optic serial communication link.
The Master station is typically speed-controlled and the other drives follow its torque
or speed reference. In general,
• Torque control of the Follower should be used when the motor shafts of the
Master and Follower drives are coupled solidly to each other by gearing, a chain
etc., so that no speed difference between the drives is possible (see illustration
below).
• Speed control of the Follower should be used when the motor shafts of the
Master and the Follower drives are coupled flexibly to each other, so that a slight
speed difference between the drives is possible (see illustration below).
In some applications, both speed control and torque control of the Followers are
required. In those cases an "on-the-fly" change between speed and torque control
can be performed via a digital input of the Follower.
Solidly coupled motor shafts:
- Speed-controlled master
- Follower follows the torque
reference of the master
External
control
signals
Mains
Supply
Supervision
Mains
Supply
Master/Follower
n
Link
3
3
2
2
Follower
Fault
3
3
Flexibly coupled motor shafts:
- Speed-controlled master
- Follower follows the speed
reference of the master
Follower follows the speed
reference of the master
External
control
signals
Master/Follower
n
Link
3
Mains
2
Supply
2
Follower
Fault
Supervision
3
Mains
Supply
49
3
3
Master/Follower