VLT
®
2800 Series
NB!:
Parameters 417-421 are only used, if in
parameter 100 Configurat ion 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 amplifi ed .
Description of choice:
Quick regulation is obtained at high amp lifi cation,
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 nee ds to achieve the same
change a s 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 deviat i ons 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 different iator does not react to a constant erro
r.
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 e rrors change.
Description of choice:
Quick control is obtained by a long different ial
time. However, if this time is too long, it ca n make
the process unstable. When the differential time
is 0 ms, the D-functio n 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 increa ses at h ighe r
frequencies, limiting the gain may be u seful. 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.28.E9.02 - VLT is a registered Danfoss trademark
102
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