Danfoss VLT AutomationDrive FC 302 Programming Manual page 114

Parameter Descriptions
7-05 Speed PID Diff. Gain Limit
Range:
parameter is used with parameter 1-00 Configuration
Mode [1] Speed closed loop control.
3 3
7-06 Speed PID Lowpass Filter Time
Range:
Size [0.1
related - 100
*
ms]
NOTICE
Severe filtering can be detrimental to dynamic
performance.
This parameter is used with parameter 1-00 Configuration
Mode [1] Speed closed loop and [2] Torque control.
Adjust the filter time in Flux Sensorless to
3-5 ms.
112
Function:
Function:
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 of noise in the system,
see Illustration 3.45. For example, if a time
constant (τ) of 100 ms is programmed, the
cut-off frequency for the low-pass filter is
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 parameter 7-06 Speed PID
Lowpass Filter Time taken from the number of
pulses per revolutions from encoder:
Encoder PPR Parameter 7-06 Speed PID
Lowpass Filter Time
512 10 ms
1024 5 ms
2048 2 ms
4096 1 ms
Danfoss A/S © Rev. 10/2014 All rights reserved.
®
VLT AutomationDrive FC 301/302
Feedback
Disturbed feedback signal
Feedback
Filtered feedback signal
Illustration 3.45 Feedback Signal
0.6
Lowpass lter
f = 10 Hz
g
0.6
t (Sec.)
t (Sec.)
MG33MJ02