Decentral Solutions
Programming, FCD
300
at slow changes and a constant differentiator gain
where quick changes to the deviation occur.
Description of choice:
Select a differentiator gain limit as required.
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.,
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, it will be dampened by the lowpass filter.
445 Flying start
(FLYING START)
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
variable frequency drive, e.g. because of an AC line
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
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 variable
frequency drive 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
’
(rotating 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
Configuration
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
influence 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.
✭
= factory setting. () = display text [] = value for use in communication via serial communication port
MG.90.F2.22 - VLT is a registered Danfoss trademark
147
