VLT
®
FCD Series
Programming, FCD
300
NB!:
Parameters 417-421 are only used, if in
parameter 100
Configuration
the selection
made is
Speed regulation, closed loop
[1].
417 Speed PID proportional gain
(SPEED PROP GAIN)
Value:
0.000 (OFF) - 1.000
✭
0.010
Function:
Proportional gain indicates how many times the
fault (deviation between the feedback signal and
the setpoint) is to be amplified.
Description of choice:
Quick regulation is obtained at high amplification,
but if the amplification is too high, the process may
become unstable in the case of overshooting.
418 Speed PID integral time
(SPEED INT. TIME)
Value:
20.00 - 999.99 ms (1000 = OFF)
✭
100 ms
Function:
The integral time determines how long the PID
regulator takes to correct the error. The greater
the error, the quicker the integrator frequency
contribution will increase. The integral time is the
time the integrator needs to achieve the same
change as the proportional amplification.
Description of choice:
Quick regulation is obtained through a short integral
time. However, if this time is too short, it can make
the process unstable. If the integral time is long,
major deviations from the required reference may
occur, since the process regulator will take long
to regulate if an error has occurred.
419 Speed PID differential time
(SPEED DIFF. TIME)
Value:
0.00 (OFF) - 200.00 ms
✭
20.00 ms
Function:
The differentiator does not react to a constant error.
It only makes a contribution when the error changes.
The quicker the error changes, the stronger the gain
from the differentiator will be. The contribution is
proportional to the speed at which errors change.
Description of choice:
Quick control is obtained by a long differential
time. However, if this time is too long, it can make
the process unstable. When the differential time
is 0 ms, the D-function is not active.
420 Speed PID D- gain limit
(SPEED D-GAIN LIM)
Value:
5.0 - 50.0
✭
5.0
Function:
It is possible to set a limit for the gain provided by the
differentiator. Since the D-gain increases at higher
frequencies, limiting the gain may be useful. This
enables obtaining a pure D-gain at low frequencies
and a constant D-gain at higher frequencies.
Description of choice:
Select the required gain limit.
421 Speed PID lowpass filter time
(SPEED FILT. TIME)
Value:
20 - 500 ms
✭
100 ms
Function:
Noise in the feedback signal is dampened by a first
order lowpass filter to reduce the noise
’
s impact on the
regulation. This might be an advantage, e.g. if there is
a great amount of noise on the signal. See drawing.
✭
= factory setting. () = display text [] = value for use in communication via serial communication port
MG.04.B7.02 - VLT is a registered Danfoss trademark
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