Danfoss FC 300 Programming Manual page 95

Parameter Descriptions
7-06 Speed PID Lowpass Filter Time
Range: Function:
Applica- [1.0 - Set a time constant for the speed control
tion 100.0 low-pass filter. The low-pass filter improves
depend- ms] steady-state performance and dampens
ent oscillations on the feedback signal. This is an
*
advantage if there is a great amount on
noise in the system, see illustration below.
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/sec.,
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 par. 7-06 Speed PID
Lowpass Filter Time taken from the number of
pulses per revolutions from encoder:
Encoder PPR
512
1024
2048
4096
Note that severe filtering can be detrimental
to dynamic performance.
This parameter is used with par. 1-00 Config-
uration Mode Speed closed loop [1] and
Torque [2] control.
The filter time in flux sensorless must be
adjusted to 3-5 ms.
FC 300 Programming Guide
Par. 7-06 Speed PID
Lowpass Filter Time
10 ms
5 ms
2 ms
1 ms
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MG.33.M9.02 - VLT is a registered Danfoss trademark
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