VLT
®
FCM Series
Function:
The integrator provides an increasing gain at a constant
error between the set point and the feedback signal.
The greater the error, the quicker the gain will increase.
The integral time is the time needed by the integrator
to reach the same gain as the proportional gain.
Used together with
Process, closed loop
mode
(parameter 100).
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.
If the integral time is long, major deviations from
the required set point may occur, since the
process regulator will take a long time to regulate
in relation to a given error.
442 Process PID differentiation time
(PROC. DIFF. TIME)
Value:
0.00 (OFF) - 10.00 sec.
[0 - 1000]
✭
0.00 sec.
[0]
Function:
The differentiator does not react to a constant error.
It only provides a gain when the error changes.
The quicker the error changes, the stronger the
gain from the differentiator.
The gain is proportional to the speed at which
the error changes.
Used together with
Process, closed loop
mode
(parameter 100).
Description of choice:
Fast regulation is obtained with a long differentiation
time. However, this time may become too long,
which can make the process unstable.
443 Process PID diff. gain limit
(PROC. DIFF. GAIN)
Value:
5.0 - 50.0
[50 - 500]
✭
5.0
[50]
Function:
It is possible to set a limit for the differentiator gain.
The differentiator gain will increase if there are fast
changes, which is why it can be beneficial to limit
this gain, thereby obtaining a pure differentiator gain
at slow changes and a constant differentiator gain
where quick changes to the error occur.
Used together with
Process, closed loop
mode
(parameter 100).
Description of choice:
Select a limit to differentiator gain as required.
444 Process PID lowpass filter time
(PROC. FILTER TIME)
Value:
0.02 - 10.00 sec
[2 - 1000]
✭
0.02 sec
[2]
Function:
Oscillations on the feedback signal are dampened by
the lowpass filter in order to reduce their impact on
the process regulation. This can be an advantage
e.g. if there is a lot of noise on the signal.
Used together with
Process, closed loop
mode
(parameter 100).
Description of choice:
Select the desired time constant (
τ
). If a time constant
(
τ
) of 100 ms is programmed, the break frequency
for the lowpass filter will be 1/0.1 = 10 RAD/sec.,
corresponding to (10/2 x
π
) = 1.6 Hz.
The process regulator will thus only regulate a feedback
signal that varies by a frequency lower than 1.6 Hz. If
the feedback signal varies by a higher frequency than
1.6 Hz, the Process regulator will not react.
445 Flying start
(FLYING START)
Value:
✭
Disable (DISABLE)
[0]
OK - same direction (OK-SAME DIRECTION)
[1]
OK - both directions (OK-BOTH DIRECTIONS)
[2]
DC-brake before start
(DC-BRAKE BEF. START)
[3]
Function:
This function makes it possible to ‘catch‘ a motor,
which is spinning freely because of a mains dropout.
✭
= factory setting. () = display text [] = value for use in communication via serial communication port
MG.03.H3.02 - VLT is a registered Danfoss trademark
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