Optimizing The Speed Controller - Siemens SINAMICS G120D Operating Instructions Manual

Advanced commissioning
7.5 Motor control
7.5.2.3

Optimizing the 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:
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:
• Acceleration pre-control scaling
• Ratio between the total and motor moment of inertia
• Proportional component K
• Integration time (integral time) TI
• Speed controller actual speed value smoothing time
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.
150
The speed setpoint (broken line) increases with the set ramp-
up time and rounding.
The actual value follows the setpoint without overshooting.
p
Operating Instructions, 04/2015, FW V4.7.3, A5E34261542B AB
p1496
p0342
Encoderless Speed control
speed control: with encoder:
p1470 p1460
p1472 p1462
p1452 p1442
Converter with control units CU250D-2