Siemens SINAMICS G115D Operating Instructions Manual page 245

How does the converter calculate the moment of inertia?
For higher speed changes, the converter 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):
J = M
If all of the following conditions are met, the converter calculates the moment of inertia:
• ① The rated accelerating torque M
– The sign of M
– M
• ② speed > p1755
• The converter has calculated the load torque in at least one direction of rotation.
• Acceleration setpoint > 8 1/s
③ The converter calculates the load torque again after acceleration.
Moment of inertia precontrol
In applications where the motor predominantly operates with a constant speed, the converter
can only infrequently calculate the moment of inertia using the function described above.
Moment of inertia precontrol is available for situations such as these. The moment of inertia
precontrol assumes that there is an approximately linear relationship between the moment of
inertia and the load torque.
SINAMICS G115D distributed drive
Operating Instructions, 09/2020, FW V4.7 SP13, A5E48681219B
- M - M
M L R
/ α
B
is the same as the direction of the actual acceleration
B
> p1560 × rated motor torque (r0333)
B
, load torque M
M
must satisfy the following two conditions:
B
(≙ speed change 480 rpm per s)
2
Advanced commissioning
6.17 Motor control
and frictional torque M
L
as
B
:
R
and
B
243