2.5 PID Control
2.5.1 Speed PID Control
1-00 Configuration Mode
1-01 Motor Control Principle
U/f
VVC
plus
[0] Speed open loop
Not Active
Not Active
[1] Speed closed loop
N.A.
ACTIVE
[2] Torque
N.A.
Not Active
[3] Process
Not Active
Not Active
Table 2.3 Control Configurations, Active Speed Control
“N.A.” means that the specific mode is not available at all. “Not Active” means that the specific mode is available but the Speed Control is not
active in that mode.
The following parameters are relevant for the Speed Control:
Parameter
Description of function
7-00 Speed PID Feedback Source Select from which input the Speed PID should get its feedback.
7-02 Speed PID Proportional Gain The higher the value - the quicker the control. However, too high value may lead to oscillations.
7-03 Speed PID Integral Time
Eliminates steady state speed error. Lower value means quicker reaction. However, too low value may
lead to oscillations.
7-04 Speed PID Differentiation
Time
Provides a gain proportional to the rate of change of the feedback. A setting of zero disables the
differentiator.
7-05 Speed PID Diff. Gain Limit
If there are quick changes in reference or feedback in a given application - which means that the error
changes swiftly - the differentiator may soon become too dominant. This is because it reacts to
changes in the error. The quicker the error changes, the stronger the differentiator gain is. The differ-
entiator gain can thus be limited to allow setting of the reasonable differentiation time for slow
changes and a suitably quick gain for quick changes.
7-06 Speed PID Lowpass Filter
Time
A low-pass filter that dampens oscillations on the feedback signal and improves steady state
performance. However, too large filter time will deteriorate the dynamic performance of the Speed PID
control.
Practical settings of parameter 7-06 taken from the number of pulses per revolution on from encoder
(PPR):
Encoder PPR
7-06 Speed PID Lowpass Filter
Time
512
10 ms
1024
5 ms
2048
2 ms
4096
1 ms
Table 2.4 Speed Control Parameters
Product Overview
VLT
®
AutomationDrive FC 360 Design Guide
24
MG06B202 - VLT
®
is a registered Danfoss trademark
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