Siemens SINAMICS G120 Operating Instructions Manual page 303

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
as the motor cannot freely rotate.
In the two cases describe above, we recommend that you manually optimize the speed control.
Optimizing the speed controller
Preconditions
● 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).
● STARTER and Startdrive have trace functions that allow the speed setpoint and actual
value to be recorded.
Procedure
1. Switch on the motor.
2. Enter a speed setpoint of approximately 40 % of the rated speed.
3. Wait until the actual speed has stabilized.
4. Increase the setpoint up to a maximum of 60 % of the rated speed.
5. Monitor the associated characteristic of the setpoint and actual speed.
Converter with the CU250S-2 Control Units
Operating Instructions, 04/2018, FW V4.7 SP10, A5E31759476B AG
The speed setpoint (broken line) increases with the set ramp-
up time and rounding.
The speed actual value follows the setpoint without any over‐
shoot.
Initially, the speed actual value follows the speed setpoint with
some delay, and then overshoots the speed setpoint.
First, the actual speed value increases faster than the speed
setpoint. Before the setpoint reaches its final value, it passes
the actual value. Finally, the actual value approaches the set‐
point without any significant overshoot.
Advanced commissioning
6.21 Motor control
301