Siemens SINAMICS G120 Operating Instructions Manual page 312
Low voltage inverters
built-in units with cu250s-2 control units and
encoder evaluation
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- List manual (1256 pages) ,
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Advanced commissioning
6.21 Motor control
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 6-61
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
You have the following options to determine the characteristic:
● You already know the characteristic from other measurements. In this case, you must set
the parameters to known values when commissioning the system.
● The inverter iteratively determines the characteristic by performing measurements while
the motor is operational.
Activating the moment of inertia estimator
The moment of inertia estimator is deactivated in the factory setting. p1400.18 = 0,
p1400.20 = 0, p1400.22 = 0.
If you performed the rotating measurement for the motor identification during quick
commissioning, we recommend leaving the moment of inertia estimator deactivated.
310
/ 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
must satisfy the following two conditions:
B
(≙ speed change 480 rpm per s)
2
+ p5313
L
+ p5315
L
Operating Instructions, 04/2018, FW V4.7 SP10, A5E31759476B AG
Converter with the CU250S-2 Control Units
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