Danfoss VLT AutomationDrive FC 301 Programming Manual page 127

Parameter Descriptions
7-03 Speed PID Integral Time
Range: Function:
8.0 [2.0 - Enter the speed controller integral time, which
ms 20000.0 determines the time the internal PID control
*
ms] takes to correct errors. The greater the error,
the more quickly the gain increases. The
integral time causes a delay of the signal and
therefore a dampening effect and can be used
to eliminate steady-state speed error. Obtain
quick control through a short integral time,
though if the integral time is too short, the
process becomes unstable. An excessively long
integral time disables the integral action,
leading to major deviations from the required
reference, since the process regulator takes
too long to regulate errors. This parameter is
used with [0] Speed open loop and [1] Speed
closed loop control, set in
parameter 1-00 Configuration Mode.
7-04 Speed PID Differentiation Time
Range: Function:
30.0 [0.0 - Enter the speed controller differentiation
ms 200.0 ms] 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 0 disables
the differentiator. This parameter is used with
parameter 1-00 Configuration Mode [1] Speed
closed loop control.
7-05 Speed PID Diff. Gain Limit
Range: Function:
5.0 [1.0 - Set a limit for the gain provided by the differ-
N/A 20.0 entiator. Consider limiting the gain at higher
*
N/A] frequencies. For example, set up a pure D-link
at low frequencies and a constant D-link at
higher frequencies. This parameter is used with
parameter 1-00 Configuration Mode [1] Speed
closed loop control.
7-06 Speed PID Lowpass Filter Time
Range: Function:
NOTICE
10.0 [1.0 -
ms 100.0
*
Severe filtering can be detrimental to
ms]
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.
MG33MO02
Programming Guide
7-06 Speed PID Lowpass Filter Time
Range:
Danfoss A/S © 01/2018 All rights reserved.
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 3.49. 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
Table 3.25 Speed PID Lowpass Filter Time
3 3
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