Danfoss VLT AutomationDrive FC 301 Series Design Manual page 27

Basic Operating Principles
Parameter
7-00 Speed PID Feedback Source
7-02 Speed PID Proportional Gain
7-03 Speed PID Integral Time
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
Program 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 nameplate 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
(referred to below 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 adjustable frequency drive limits are set to safe values
MG33BF22
Design Guide
Description of function
Select from which input the speed PID should get its feedback.
The higher the value, the quicker the control. However, too high value may lead to
oscillations.
Eliminates steady state speed error. Lower value means quick reaction. However, too
high 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 differentiator 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, a filter time that is too long causes the dynamic
performance of the speed PID control to deteriorate.
Practical settings of parameter 7-06 taken from the number of pulses per revolution from
encoder (PPR):
Encoder PPR
512
1024
2048
4096
The adjustable frequency drive 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 Setting
1-2* As specified by motor nameplate
1-29 Automatic [1] Enable complete AMA
Motor Adaptation
(AMA)
Set a positive reference.
16-20 Motor Angle N.A. (read-only parameter) Note: An increasing value
overflows at 65,535 and starts again at 0.
5-71 Term 32/33 [1] Counter-clockwise (if 16-20 Motor Angle is decreasing)
Encoder Direction
Rev. 2014-04-04 All rights reserved.
7-06 Speed PID Lowpass Filter Time
10 ms
5 ms
2 ms
1 ms
3 3
25