ABB ACS880 Series, Firmware Manual

Page: 89 / 764

After these conditions have been fulfilled, autotuning can be activated by parameter
25.33 (or the signal source selected by it).
Autotune modes
Autotuning can be performed in three different ways depending on the setting of
parameter
25.34 . The selections Smooth , Normal and Tight define how the drive
torque reference should react to a speed reference step after tuning. The selection
Smooth will produce a slow but robust response; Tight will produce a fast response
but possibly too high gain values for some applications. The figure below shows
speed responses at a speed reference step (typically 1…20%).
n/n
N
%
t
A
B
C
D
Undercompensated A
Normally tuned (autotuning) B
Normally tuned (manually). Better dynamic performance than with B C
Overcompensated speed controller D
Autotune results
At the end of a successful autotune routine, its results are automatically transferred
into parameters
• 25.2 (proportional gain of the speed controller)
• 25.3 (integration time of the speed controller)
• 25.37 (mechanical time constant of the motor and machine).
Nevertheless, it is still possible to manually adjust the controller gain, integration
time and derivation time.
Program features 89