Danfoss VLT AutomationDrive FC 300 Programming Manual page 130

FC 300 Programming Guide
7-04 Speed PID Differentiation Time
Range:
Application [0.0 - 200.0 ms]
dependent*
7-05 Speed PID Diff. Gain Limit
Range:
5.0* [1.0 - 20.0 ]
7-06 Speed PID Lowpass Filter Time
Range:
Application [1.0 - 100.0 ms]
dependent*
Function:
Enter the speed controller differentiation time. The differentiator does not react to constant error.
It provides gain proportional to the rate of change of the speed feedback. The quicker the error
changes, the stronger the gain from the differentiator. The gain is proportional with the speed at
which errors change. Setting this parameter to zero disables the differentiator. This parameter is
Configuration Mode Speed closed loop
used with par. 1-00
Function:
Set a limit for the gain provided by the differentiator. Since the differential gain increases at higher
frequencies, limiting the gain may be useful. For example, set up a pure D-link at low frequencies
and a constant D-link at higher frequencies. This parameter is used with par. 1-00
Mode Speed closed loop [1] control.
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 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.
Speed PID Lowpass Filter Time
Practical settings of par. 7-06
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
control.
The filter time in flux sensorless must be adjusted to 3-5 ms.
®
MG.33.M8.02 - VLT is a registered Danfoss trademark
3 Parameter descriptions
[1] control.
taken from the number of pulses per
Par. 7-06 Speed PID Lowpass Filter Time
10 ms
5 ms
2 ms
1 ms
Configuration Mode Speed closed loop
3
Configuration
Torque
[1] and [2]
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