Speed Pid Control; The Following Parameters Are Relevant For The Speed Control - Danfoss FC 300 Design Manual

FC 300 Design Guide

Speed PID Control

The table shows the control configurations where the Speed Control is active.
Par. 1-00 Configura- Par. 1-01 Motor Control Principle
tion Mode
U/f
[0] Speed open loop Not Active
[1] Speed closed loop N.A.
[2] Torque N.A.
[3] Process
Note: "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.
Note: The Speed Control PID will work under the default parameter setting, but tuning the parameters
is highly recommended to optimize the motor control performance. The two Flux motor control principles
are specially dependant on proper tuning to yield their full potential.

The following parameters are relevant for the Speed Control:

Parameter
Feedback Par. 7-00
Proportional Gain
7-02
Integral Time Par. 7-03
Differentiation Time Par.
7-04
Differentiator Gain Limit
Par. 7-05
Lowpass Filter Time Par.
7-06
Below is given an example of how to programme the Speed Control:
In this case the Speed PID Control is used to
maintain a constant motor speed regardless of the
changing load on the motor.
The required motor speed is set via a potentiom-
eter connected to terminal 53. The speed range is
0 - 1500 RPM corresponding to 0 - 10V over the
potentiometer.
Starting and stopping is controlled by a switch
connected to terminal 18.
The Speed PID monitors the actual RPM of the
motor by using a 24V (HTL) incremental encoder
In the parameter list below it is assumed that all other parameters and switches remain at their default
setting.
Introduction to FC 300
VVCplus
Not Active
ACTIVE
N.A.
Not Active
Description of function
Select from which input the Speed PID should get its feedback.
Par. 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. How-
ever, 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 differen-
tiation time for slow changes and a suitably quick gain for quick changes.
A low-pass filter that dampens oscillations on the feedback signal and im-
proves steady state performance. However, too large filter time will deterio-
rate the dynamic performance of the Speed PID control.
Practical settings of Par 7-06 taken from the number of pulses per revolution
on from encoder (PPR):
Encoder PPR
512
1024
2048
4096
MG.33.B7.02 - VLT is a registered Danfoss trademark
Flux Sensorless
ACTIVE
N.A.
N.A.
ACTIVE
Par. 7-06
10 ms
5 ms
2 ms
1 ms
as feedback. The feedback sensor is an encoder
(1024 pulses per. revolution) connected to termi-
nals 32 and 33.
Flux w/ enc. feedb
N.A.
ACTIVE
Not Active
ACTIVE
29