ABB ACS850 Firmware Manual page 45

The figure below shows speed responses at a speed reference step (typically
1...20%).
n
%
n
N
A
A: Undercompensated
B: Normally tuned (autotuning)
C: Normally tuned (manually). Better dynamic performance than with B
D: Overcompensated speed controller
The figure below is a simplified block diagram of the speed controller. The controller
output is the reference for the torque controller.
Speed
reference
Calculated actual
B
Error
+
-
value
speed
Program features 45
C D
Derivative
acceleration
compensation
Proportional,
+
integral
+
+
Derivative
t
Torque
reference