ABB ACS880 Firmware Manual page 328

328 Parameters
No. Name / Range /
Selection
25.4 Speed derivation
time
0.000 ... 10.000 s
25.5 Derivation filter time
0...10000 ms
Description
Defines the derivation time of the speed controller.
Derivative action boosts the controller output if the
error value changes.
The longer the derivation time, the more the speed
controller output is boosted during the change. If the
derivation time is set to zero, the controller works as
a PI controller, otherwise as a PID controller. The
derivation makes the control more responsive for
disturbances. For simple applications (especially those
without an encoder), derivative time is not normally
required and should be left at zero.
The figure below shows the speed controller output
after an error step when the error remains constant.
The speed error derivative must be filtered with a low
pass filter to eliminate external disturbances.
%
e
K × T ×
p D
T
K × e
s
p
K × e
p
Gain = K = 1
p
T = Integration time > 0
I
T = Derivation time > 0
D
T = Sample time period = 500 μs
s
Δe = Error value change between two samples
Derivation time for speed controller.
Defines the derivation filter time constant. See
parameter 25.4 Speed derivation
Derivation filter time constant.
Controller
output
Error value
e = Error value
T
I
Time
time.
Def / Type
FbEq 16b / 32b
0.000 s / real32
1000 = 1 s / 1000 = 1
s
8 ms / real32
1 = 1 ms / 1 = 1 ms