Danfoss VLT AutomationDrive FC 301 Design Manual page 26

Basic Operating Principles
Parameter
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
3 3
7-04 Speed PID Differentiation
Time
7-05 Speed PID Diff. Gain Limit
7-06 Speed PID Lowpass Filter
Time
7-07 Speed PID Feedback Gear
Ratio
7-08 Speed PID Feed Forward
Factor
7-09 Speed PID Error Correction
w/ Ramp
Table 3.2 Relevant Parameters for Speed Control
Programme in the order shown (see explanation of settings in the Programming Guide)
In Table 3.3 it is assumed that all other parameters and switches remain at their default setting.
Function
1) Make sure the motor runs properly. Do the following:
Set the motor parameters using name plate data
Perform an Automatic Motor Adaptation
2) Check the motor is running and the encoder is attached properly. Do the following:
Press [Hand On] on the LCP. Check that the motor is
running and note in which direction it is turning
(henceforth referred to as the "positive direction").
Go to 16-20 Motor Angle. Turn the motor slowly in the
positive direction. It must be turned so slowly (only a
few RPM) that it can be determined if the value in
16-20 Motor Angle is increasing or decreasing.
If 16-20 Motor Angle is decreasing, change the encoder
direction in 5-71 Term 32/33 Encoder Direction.
3) Make sure the frequency converter limits are set to safe values
Set acceptable limits for the references.
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VLT AutomationDrive FC 301/FC 302 Design Guide, 0.25-75 kW
Description of function
Eliminates steady state speed error. Lower value means quick reaction. However, too low value may
lead to oscillations.
Provides a gain proportional to the rate of change of the feedback. A setting of zero disables the
differentiator.
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.
A low-pass filter that dampens oscillations on the feedback signal and improves steady state
performance. However, too large filter time deteriorates 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
The frequency converter multiplies the speed feedback by this ratio.
The reference signal bypasses the speed controller by the amount specified. This feature increases the
dynamic performance of the speed control loop.
The speed error between ramp and actual speed is held up against the setting in this parameter. If the
speed error exceeds this parameter entry, the speed error is corrected via ramping in a controlled way.
Parameter
1-2*
1-29 Automatic
Motor Adaptation
(AMA)
16-20 Motor Angle N.A. (read-only parameter) Note: An increasing value
5-71 Term 32/33
Encoder Direction
3-02 Minimum
Reference
3-03 Maximum
Reference
MG33BF02 - Rev. 2013-12-20
Setting
As specified by motor name plate
[1] Enable complete AMA
Set a positive reference.
overflows at 65535 and starts again at 0.
[1] Counter clockwise (if 16-20 Motor Angle is decreasing)
0 RPM (default)
1500 RPM (default)