Siemens SINAMICS S120 Function Manual page 584

Function modules
8.12 Moment of inertia estimator
Determining the load torque
The load torque must first be determined to determine the moment of inertia.
Phases with constant speed not equal to zero are required to determine the load torque (e.g.
friction force). For small speed changes, the converter calculates the load torque M
actual motor torque. The following conditions must be satisfied to do this:
● Speed ≥ p1226
● Acceleration setpoint < 8 1/s
● Acceleration · moment of inertia (r1493) < 0.9 · p1560.
After determining the load torque, the moment of inertia can be determined in the
acceleration phases. If the source of p1502 has a 1 signal, the moment of inertia is not
estimated.
The accuracy of the moment of inertia estimation increases as the acceleration rate
increases. The start value of the moment of inertia estimator is the parameterized moment of
inertia (J = p0341 · p0342 + p1498).
584
2
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
from the
L
Drive functions