ABB ACS880 - Page 328

Def / Type
FbEq 16b / 32b
DescriptionName / Range /
Selection
No.
0.000 s / real32Defines 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.
K
p
×e
K
p
× T
D
×
'e
T
s
T
I
K
p
×e
%
Controller
output
Error value
e = Error value
Time
Gain = K
p
= 1
T
I
= Integration time > 0
T
D
= Derivation time > 0
T
s
= Sample time period = 500 μs
Δe = Error value change between two samples
Speed derivation
time
25.4
1000 = 1 s / 1000 = 1
s
Derivation time for speed controller.0.000 ... 10.000 s
8 ms / real32Defines the derivation filter time constant. See
parameter 25.4 Speed derivation time.
Derivation filter time25.5
1 = 1 ms / 1 = 1 msDerivation filter time constant.0...10000 ms
328 Parameters