PID process control, continued:
The Proportional gain, Integration time and Differen-
tiation time of the process controller are set in individ-
ual parameters, and the setting ranges are adapted to
process control requirements.
As in speed control, it is possible to limit the influence
of the differentiator in relation to swift changes in the
error between the reference and the feedback signal.
Also available is a lowpass filter for the process con-
troller. This can be set to remove a much greater share
of the feedback signal oscillations than the lowpass
filter of the speed controller does. This is because most
fans and pump applications react relatively slowly,
which is why it can be an advantage to feed as stable
a signal as possible to the process controller.
The parameters that are specific to the process con-
troller are parameters 437 to 444.
Setting of torque controller (open loop):
This control is selected if Torque control, open loop
has been selected in 100 Configuration.
When this mode has been selected, the reference will
use the Nm unit.
Control is in the form of a PI that requires no feedback,
since the torque is calculated on the basis of the cur-
rent measurement of VLT 5000. The proportional gain
is set as a percentage in parameter 433 Torque pro-
portional gain and the integration time is set in param-
eter 434 Torque integration time. However, both these
have been set at the works and normally require no
modification.
VLT
®
5000 Series
MG.51.C5.22 - VLT
p
is a registered Danfoss trademark. 173
Examples of use
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