Siemens SINAMICS G120 Operating Instructions Manual page 311

How does the inverter calculate the load torque?
Figure 6-59
At low speeds, the inverter calculates the load torque M
The calculation takes place under the following conditions:
● Speed ≥ p1226
● Acceleration setpoint < 8 1/s
● Acceleration × moment of inertia (r1493) < 0.9 × p1560
How does the inverter calculate the moment of inertia?
Figure 6-60
For higher speed changes, the inverter initially calculates the accelerating torque M
difference between the motor torque M
M = M
B
Moment of inertia J of the motor and load is obtained from the accelerating torque M
angular acceleration α (α = rate at which the speed changes):
Converter with the CU250S-2 Control Units
Operating Instructions, 04/2018, FW V4.7 SP10, A5E31759476B AG
Calculating the load torque
Calculating the moment of inertia
- M - M
M L R
(≙ speed change 480 rpm per s)
2
, load torque M
M
Advanced commissioning
6.21 Motor control
from the actual motor torque.
L
and frictional torque M
L
as
B
:
R
and
B
309