VLT
®
4000 VT
if there is a deviation between reference/setpoint
and the actual process state.
Used in
Closed loop
[1] (parameter 100).
Description of choice:
If the AFD is to reduce the output frequency in case
the feedback signal increases, select
Normal
[0].
If the AFD is to increase the output frequency in case
the feedback signal increases, select
Inverse
[1].
421 PID anti windup
(PID ANTI WINDUP)
Value:
Off (DISABLE)
[0]
✭
On (ENABLE)
[1]
Function:
It is possible to choose whether the process regulator
is to continue regulating on a deviation even if it is not
possible to increase/reduce the output frequency.
Used in
Closed loop
[1] (parameter 100).
Description of choice:
The factory setting is
On
[1], which means that
the integration link is adjusted to the actual output
frequency if either the current limit, the voltage limit
or the max./min. frequency has been reached. The
process regulator will not be engaged again, until either
the deviation is zero or its prefix has changed.
Select
Off
[0] if the integrator is to continue
integrating to the deviation even if it is not possible
to remove the deviation by regulation.
NOTE
If
Off
[0] is selected, it will mean that when
the deviation changes its prefix, the integrator
will first have to integrate down from the level
obtained as a result of the former error, before any
change to the output frequency occurs.
422 PID start-up frequency
(PID START VALUE)
Value:
f
MIN
-f
MAX
(parameter 201 and 202)
✭
0 Hz
Function:
When the start signal comes, the AFD will react in the
form of
Open loop
[0] following the ramp. Only when the
programmed start frequency has been obtained, will it
change over to
Closed loop
[1]. In addition, it is possible
to set a frequency that corresponds to the speed at
which the process normally runs, which will enable the
required process conditions to be reached sooner.
Used in
Closed loop
[1] (parameter 100).
Description of choice:
Set the required start frequency.
NOTE
If the AFD is running at the current limit before
the desired start frequency is obtained, the
process regulator will not be activated. For the
regulator to be activated anyway, the start frequency
must be lowered to the required output frequency.
This can be done during operation.
NOTE
PID start frequency is always applied in
clockwise direction.
423 PID proportional gain
(PID PROP. GAIN)
Value:
0.00 - 10.00
✭
0.01
Function:
The proportional gain indicates the number of times
the deviation between the reference/setpoint and
the feedback signal is to be applied.
Used in
Closed loop
[1] (parameter 100).
Description of choice:
Quick regulation is obtained by a high gain, but if the
gain is too high, the process may become unstable.
424 PID integration time
(PID INTEGR.TIME)
Value:
0.01 - 9999.00 sec. (OFF)
✭
OFF
Function:
The integrator provides a constant change of the
output frequency during constant error between the
reference/setpoint and the feedback signal. The
greater the error, the quicker the integrator frequency
contribution will increase. The integration time is the
MG.40.A7.22 - VLT is a registered Danfoss trademark
106
