Siemens SINAMICS S150 NEMA, Operating Instructions Manual, Page: 630 / 862

Functions, monitoring and protective functions
9.4 Extended functions
Enclosed Drives
628
Operating Instructions, 12/2018, A5E36652151A
9.4.5 Moment of inertia estimator
Background
From the load moment of inertia and the speed setpoint change, the converter calculates the
accelerating torque required for the motor. Via the speed controller precontrol, the
accelerating torque specifies the main percentage of the torque setpoint. The speed
controller corrects inaccuracies in the precontrol (feed-forward control).
Figure 9-27 Influence of the moment of inertia estimator on the speed control
The more precise the value of the moment of inertia in the converter, the lower the overshoot
after speed changes.
Figure 9-28 Influence of the moment of inertia estimator on the speed
Function
From the actual speed, the actual motor torque and the frictional torque of the load, the
converter calculates the total moment of inertia of the load and motor.
Figure 9-29 Overview of the function of the moment of inertia estimator