7-04 Speed PID Differentiation Time
Range: Function:
tiator. The gain is proportional with the
speed at which errors change. Setting
this parameter to zero disables the
differentiator. This parameter is used
with 1-00 Configuration Mode Speed
closed-loop [1] control.
Application
dependent*
[0.0 -
200.0
ms]
Enter the speed controller differentiation
time. The differentiator does not react to
constant error. It provides gain propor-
tional to the rate of change of the speed
feedback. The quicker the error changes,
the stronger the gain from the differen-
tiator. The gain is proportional with the
speed at which errors change. Setting
this parameter to zero disables the
differentiator. This parameter is used
with 1-00 Configuration Mode Speed
closed-loop [1] control.
7-05 Speed PID Diff. Gain Limit
Range: Function:
5.0* [1.0 -
20.0 ]
Set a limit for the gain provided by the differ-
entiator. 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
1-00 Configuration Mode Speed closed-loop [1]
control.
7-06 Speed PID Lowpass Filter Time
Range: Function:
Application
dependent*
[1.0 -
100.0
ms]
Application
dependent*
[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 figure 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 frequency
7-06 Speed PID Lowpass Filter Time
Range: Function:
higher 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
1,024 5 ms
2,048 2 ms
4,096 1 ms
Note that severe filtering can be
detrimental to dynamic performance.
This parameter is used with 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.
Parameter Descriptions FC 300 Programming Guide
MG33MD22 - VLT
®
is a registered Danfoss trademark 3-79
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