Danfoss VLT CDS302 User Manual

6.8 Parameters: 7-** Controllers
7-06 Speed PID Lowpass Filter Time
Range: Function:
Size
related*
[1.0 -
100.0
ms]
Set a time constant for the speed control
low-pass filter. The low-pass filter improves
steady-state performance and dampens
oscillations on the feedback signal. This is an
advantage if there is a great amount on
noise in the system, see Illustration 6.9. For
example, if a time constant (τ) of 100 ms is
programmed, the cut-off frequency for the
low-pass filter will be 1/0.1= 10 RAD/s.,
corresponding to (10/2 x π) = 1.6 Hz. The
PID regulator only regulates a feedback
signal that varies by a frequency of less than
1.6 Hz. If the feedback signal varies by a
higher frequency than 1.6 Hz, the PID
regulator does not react.
Practical settings of 7-06 Speed PID Lowpass
Filter Time taken from the number of pulses
per revolutions from encoder:
Encoder PPR 7-06 Speed PID
Lowpass Filter Time
512 10 ms
1024 5 ms
2048 2 ms
4096 1 ms
Table 6.9
NOTE
Severe filtering can be detrimental to dynamic
performance.
This parameter is used with 1-00 Configuration Mode [1]
Speed closed loop and [2] Torque control.
The filter time in flux sensorless must be adjusted to
3-5 ms.
0.6
0.6
f
g
= 10 Hz
175ZA293.11
Feedback
Disturbed feedback signal
t (Sec.)
t (Sec.)
Filtered feedback signal
Lowpass lter
Feedback
Illustration 6.9
6.8.1
7-2* Process PID Feedback
Select the feedback sources for the Process PID Control,
and how this feedback should be handled.
7-20 Process CL Feedback 1 Resource
Option: Function:
For process loop with
current input, 54 switch has
to be positionned on I
(current).
[0] No function
[1] Analog input 53
Parameter Descriptions
Operating Instructions VLT
®
CDS302 and CDS303
MG34M302 - VLT
®
is a registered Danfoss trademark/Commercial Compressor 73
6
6

Danfoss VLT CDS302 Specifications

General

Brand	Danfoss
Model	VLT CDS302
Category	DC Drives
Language	English