Fantech VLT 2800 Series Instruction Manual page 74

441 Process PID integration time
(PROC. INTEGR. T.)
Value:
0.01 - 9999.99 (OFF)
Function:
The integrator provides an increasing gain at a constant
error between the reference/setpoint and the feedback
signal. The greater the error, the quicker the integrator
frequency contribution will increase.The integral time
is the time needed by the integrator to make the
same change as the proportional 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 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.
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 differentiation
time. However, this time may become too long, which
can make the process unstable due to overswing.
443 Process PID diff. gain limit
(PROC. DIFF.GAIN)
Value:
5.0 - 50.0
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 a pure differentiator gain is obtained
= factory setting. () = display text [] = value for use in communication via serial communication port
MG.28.A8.22 - VLT is a registered Danfoss trademark
VLT® 2800 Series
at slow changes and a constant differentiator gain
where quick changes to the deviation occur.
Description of choice:
OFF
Select a differentiator gain limit as required.
444 Process PID lowpass filter time
(PROC FILTER TIME)
Value:
0.02 - 10.00
Function:
Noise in the feedback signal is dampened by a first
order lowpass filter to reduce the noise's impact on
the process regulation. This can be an advantage
e.g. if there is a lot of noise on the signal.
Description of choice:
Select the required time constant (t). If a time constant
(t) of 0.1 s is programmed, the cut-off 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
0.00 sec.
Hz, it will be dampened by the lowpass filter.
445 Flying start
(FLYING START)
Value:
Off (DISABLE)
OK - same direction
(OK-SAME DIRECTION)
OK - both directions
(OK-BOTH DIRECTIONS)
DC brake and start
(DC-BRAKE BEF. START)
Function:
This function makes it possible to 'catch' a rotating
motor shaft, which is no longer controlled by the
variable frequency drive, e.g. because of an AC line
5.0
drop-out. The function is activated each time a start
command is enabled. For the variable frequency
drive to be able to 'catch' the rotating motor shaft,
the motor speed must be lower than the frequency
0.02
[0]
[1]
[2]
[3]
73