Siemens Sinamics CU240D-2 DP Operating Instructions Manual page 211

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):
J = M
If all of the following conditions are met, the inverter calculates the moment of inertia:
①
●
– The sign of M
– M
②
●
● The inverter has calculated the load torque in at least one direction of rotation.
● Acceleration setpoint > 8 1/s
③
The inverter calculates the load torque again after acceleration.
Moment of inertia precontrol
In applications where the motor predominantly operates with a constant speed, the inverter
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.
Example: For a horizontal conveyor, in a first approximation, the moment of inertia depends
on the load.
Figure 6-48
The relationship between load torque and torque is saved in the inverter as linear
characteristic.
● In a positive direction of rotation:
Moment of inertia J = p5312 × load torque M
● In a negative direction of rotation:
Moment of inertia J = p5314 × load torque M
Converter with the control units CU240D-2
Operating Instructions, 04/2018, FW V4.9 SP10, A5E34262100B AF
- M - M
M L R
/ α
B
The rated accelerating torque M
is the same as the direction of the actual acceleration
B
> p1560 × rated motor torque (r0333)
B
speed > p1755
Moment of inertia precontrol
, load torque M
M
must satisfy the following two conditions:
B
(≙ speed change 480 rpm per s)
2
+ p5313
L
+ p5315
L
Advanced commissioning
6.15 Motor control
and frictional torque M
L
as
B
:
R
and
B
209