Technical data

444 Process PID lowpass filter time
(proc filter time)
Value:
0.02 - 10.00
0.02
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., correspond-
ing to (10 / 2 x ) = 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, it will be
dampened by the lowpass filter.
445 Flying start
(flyingstart)
Value:
Off (DISABLE) [0]
OK - same direction
(OK-same direction) [1]
OK - both directions
(OK-both directions) [2]
DC brake and start
(DC-BRAKE BEF. START) [3]
Function:
This function makes it possible to 'catch' a rotating
motor shaft, which is no longer controlled by the fre-
quency converter, e.g. because of a mains drop-out.
The function is activated each time a start command
is enabled. For the frequency converter to be able to
'catch' the rotating motor shaft, the motor speed must
be lower than the frequency that corresponds to the
frequency in parameter 202 Output frequency, high
limit, f
MAX
.
Description of choice:
Select Disable [0] if this function is not required.
Select OK - same direction [1] if the motor shaft is only
able to rotate in the same direction when cutting in. OK
- same direction [1] should be selected if in parameter
200 Output frequency range a selection has been of
Clockwise only .
Select OK - both directions [2] if the motor is able to
rotate in both directions when cutting in.
Select DC brake and start [3] if the frequency converter
is to be able to brake the motor using the DC brake
first, followed by start. It is assumed that parameters
126-127/132 DC brake are enabled. In the case of
higher 'Windmilling' (rotating motor) effects, the fre-
quency converter is not able to 'catch' a rotating motor
without selecting DC brake and start .
Limitations:
-
Too low inertia will lead to load acceleration,
which can be dangerous or prevent correct
catching of a rotating motor. Use the DC
brake instead.
-
If the load is driven, e.g. by 'Windmilling' (ro-
tating motor) effects, the unit may cut out
because of overvoltage.
-
Flying start does not work at lower values
than 250 rpm.
451 Speed PID feedforward factor
(feedforward fact)
Value:
0 - 500 %
100 %
Function:
This parameter is only active if in parameter 100 Con-
figuration the selection made is Speed regulation,
closed loop. The FF function sends a larger or smaller
part of the reference signal outside the PID controller
in such a way that the PID controller only has an influ-
ence on part of the control signal. Any change to the
set point will thus have a direct effect on the motor
speed. The FF factor provides high dynamism when
changing the set point and less overswing.
Description of choice:
The required % value can be selected in the interval f
MIN
- f
MAX
. Values over 100 % are used if the set point
variations are only small.
VLT
®
2800 Series
= factory setting, () = display text, [] = value for use in communication via serial communication port
MG.27.E3.02 - VLT
®
is a registered Danfoss trademark 107
Programming