ABB ACS850 - Page 45

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