Siemens CU240B-2 - Optimizing the Closed-Loop Speed Controller

Advanced commissioning
6.5 Motor control
Converter with the CU240B-2 and CU240E-2 Control Units
248 Operating Instructions, 01/2016, FW V4.7 SP6, A5E34259001B AC
6.5.2.2
Optimizing the closed-loop speed controller
Optimum control response - post optimization not required
Preconditions for assessing the controller response:
● The moment of inertia of the load is constant and does not depend on the speed
● The inverter does not reach the set torque limits during acceleration
● You operate the motor in the range 40 % … 60 % of its rated speed
If the motor exhibits the following response, the speed control is well set and you do not
have to adapt the speed controller manually:
The speed setpoint
(broken line) increases with the set ramp-
up time and rounding.
The actual value follows the setpoint without overshooting.
Control optimization required
In some cases, the self-optimization result is not satisfactory or self-optimization is not
possible because the motor cannot rotate freely.
In these cases, you must optimize the closed-loop speed control manually. The following
parameters influence the response of the speed control:
•
p1496
•
p0342
•
p1470
•
p1472
•
p1452
Acceleration pre
-control scaling
Ratio between the total and motor moment of inertia
P gain K
P
Integration time (integral time) T
I
Speed controller actual speed value smoothing time (without encoder)
Optimizing the speed controller
Requirements
● Torque precontrol is active: p1496 = 100 %.
● The load moment of inertia is constant and independent of the speed.
● The inverter requires 10 % … 50 % of the rated torque to accelerate.
When necessary, adapt the ramp-up and ramp-down times of the ramp-function
generator (p1120 and p1121).
● You have prepared the trace function in STARTER or Startdrive to be able to trace the
speed setpoint and the speed actual value.