Parameters: 7-** Controllers - Danfoss VLT Midi Drive FC 280 Programming Manual

Parameter Descriptions

4.8 Parameters: 7-** Controllers

7-00 Speed PID Feedback Source
Option:
4 4
[1] 24V encoder
[6] Analog Input 53
[7] Analog Input 54
[8] Frequency input 29
[9] Frequency input 33
[20] None
*
7-02 Speed PID Proportional Gain
Range:
0.015 [0 -
*
1 ]
7-03 Speed PID Integral Time
Range:
8 [2 -
ms 20000
*
ms]
7-04 Speed PID Differentiation Time
Range:
30 [0 -
ms 200 ms]
*
66
VLT
Function:
NOTICE
This parameter cannot be
changed while the motor is
running.
Select feedback source for speed CL
control.
Function:
Enter the speed controller proportional gain. The
proportional gain amplifies the error (that is the
deviation between the feedback signal and the
setpoint). This parameter is used with
parameter 1-00 Configuration Mode [1] Speed closed
loop control. Quick control is obtained at high
amplification. However, if the amplification is too
high, the process may become unstable.
Function:
Enter the speed controller integral time, which
determines the time the internal PID 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 [1] Speed closed loop control set in
parameter 1-00 Configuration Mode.
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
Danfoss A/S © 07/2016 All rights reserved.
®
Midi Drive FC 280
7-04 Speed PID Differentiation Time
Range:
7-05 Speed PID Diff. Gain Limit
Range:
5 [1 -
*
20 ]
7-06 Speed PID Lowpass Filter Time
Range:
10 [1 -
ms 6000
*
ms]
Function:
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 Configu-
ration Mode [1] Speed closed loop control.
Function:
Set a limit for the gain provided by the differen-
tiator. 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 parameter 1-00 Configuration
Mode [1] Speed closed loop control.
Function:
NOTICE
Severe filtering can be detrimental to
dynamic performance.
This parameter is used with
parameter 1-00 Configuration Mode [1]
Speed closed loop.
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 parameter is useful if there is
a great amount of noise in the system, see
Illustration 4.15. For example, if a time constant (τ)
of 100 ms is programmed, the cutoff 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
MG07C302