Technical data

VLT
®
2800 Series
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
(SPEEDD-GAINLIM)
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.
Description of choice:
If a time constant (t) of 100 ms is programmed, the
cut-off frequency for the lowpass filter will be 1/0.1 =
10 RAD/sec., corresponding to (10 / 2 x π)=1.6Hz.
The PID regulator will then only regulate a feedback
signal that varies with a frequency of less 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.
423 U1 voltage
(U1 VOLTAGE)
Value:
0.0 - 999.0 V
✭ par. 103
Function:
Parameters 423-428 are used when in parameter
101 Torque c haracteristic a selection has be
en made
of Special motor characteristic [8]. It is possible to
determine a U/f characteristic on the basis of four
definable voltages and three frequencie
s. The voltage
at 0 Hz is set in parameter 133 Start voltage.
✭ = factory setting. () = display text [] = value for use in communication via serial communication port
MG.28.A9.02 - VLT is a registered Danfoss trademark
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