Danfoss VLT AutomationDrive FC 301 Programming Manual page 125

Parameter Descriptions
7-03 Speed PID Integral Time
Range: Function:
Size [1.0 - Enter the speed controller integral time,
related 20000 which determines the time the internal PID
*
ms] control 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:
Size [0 - Enter the speed controller differentiation
related 200 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 differen-
tiator. The gain is proportional with the
speed at which errors change. Setting this
parameter to zero disables the differen-
tiator. 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 [1 - Set a limit for the gain provided by the differen-
*
20] tiator. Consider limiting the gain at higher
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.
MG33ML02
Programming Guide
7-06 Speed PID Lowpass Filter Time
Range:
Size
related
*
Danfoss A/S © 02/2016 All rights reserved.
Function:
NOTICE
[0.1
- 100
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.
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 3.47. 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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