VLT
®
FCD Series
NB!:
If Disable [0] is selected, it will mean that
when the deviation changes its sign, the inte-
grator will first have to integrate down from the level
obtained as a result of the former error, before any
change in output frequency occurs.
439
439 Process PID start frequency
(PROC START VALUE)
Value:
f
MIN
-f
MAX
(parameter 201/202)
✭ Par. 201 Output frequency, low limit, f
MIN
Function:
When the start signal comes, the frequency con-
verter will react in the form of Open loop and will not
change to Closed loop until the programmed start
frequency is reached. This makes it possible to set a
frequency that corresponds to the speed at which
the process normally runs, which will enable the re-
quired process conditions to be reached sooner.
Description of choice:
Set the required start frequency.
NB!:
If the frequency converter is running a the cur-
rent limit before the required start frequency is
obtained, the process regulator will not be activated.
For the regulator to be activated anyway, the start
frequency must be lower to the required output fre-
quency. This can be done during operation.
440
440 Proces PID proportioanl gain
(PROC. PROP. GAIN)
Value:
0.0 - 10.00
✭ 0.01
Function:
The proportional gain indicates the number of times
the deviation between the setpoint and the feedback
signal is to be applied.
Description of choice:
Quick regulation is obtained by a high gain, but if the
gain is too high, the process may become unstable
due to overshoot.
441
441 Process PID integration time
(PROC. INTEGR. T.)
Value:
0.01 - 9999.99 (OFF)
✭ OFF
Function:
The integrator provides an increasing gain at a con-
stant error between the reference/setpoint and the
feedback signal. The greater the error, the quicker
the integrator frequency contribution will in-
crease.The integral time is the time needed by the
integrator to make the same change as the propor-
tional gain.
Description of choice:
Quick regulation is obtained at a short integral time.
However, this time may become too short, which can
make the process unstable due to overswing. If the
integral time is long, major deviations from the
required setpoint may occur, since the process regu-
lator will take a long time to regulate in relation to a
given error.
442
442 Process PID differentiation time
(PROC. DIFF. TIME)
Value:
0.00 (OFF) - 10.00 sec.
✭ 0.00 sec.
Function:
The differentiator does not react to a constant error.
It only makes a gain when an error changes. The
quicker the deviation changes, the stronger the gain
from the differentiator. The gain is proportional to
the speed at which the deviation changes.
Description of choice:
Quick regulation is obtained with a long differentia-
tion time. However, this time may become too long,
✭
= factory setting. () = display text [] = value for use in communication via serial communication port
MG.04.A1.02 - VLT is a registered Danfoss trade mark
91
Programming
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