Siemens SIMATIC Manual page 49

Example of Weakening the Control Response with PFAC_SP
Process parameters:
•
GAIN = 6
•
T1
•
T2
Controller parameters:
•
GAIN = 1.45
•
TI
Process value
The figure below shows three attempts each with a setpoint step change from
0 to 60:
Attempt PFAC_SP
Left 8:18 1.0
Middle 8:19 0.8
Right 8:20 0.0
PID Temperature Control
A5E00125039-02
= 50 s
= 5 s;
= 19.6 s
Comment
No P-action in the feedback;
undamped control response
20% P-action in the feedback;
optimum control response
Complete P-action in the feedback;
too strongly damped, long transient response
Controller Tuning in FB 58 "TCONT_CP"
Setpoint
Process value
Manip. variable
Overshoot
32 %
2 %
-
3-17