Friction Characteristic - Siemens SINAMICS G120 Operating Instructions Manual

Advanced commissioning
6.21 Motor control
6.21.3.6

Friction characteristic

Function
In many applications, e.g. applications with geared motors or belt conveyors, the frictional
torque of the load is not negligible.
The inverter provides the possibility of precontrolling the torque setpoint, bypassing the speed
controller. The precontrol reduces overshooting of the speed after speed changes.
Figure 6-54
The inverter calculates the current frictional torque from a friction characteristic with 10
intermediate points.
Figure 6-55
The intermediate points of the friction characteristic are defined for positive speeds. In the
negative direction of rotation, the inverter uses the intermediate points with a negative sign.
Recording a friction characteristic
After quick commissioning, the inverter sets the speeds of the intermediate points to values
suitable for the rated speed of the motor. The frictional torque of all intermediate points is still
equal to zero. On request, the inverter records the friction characteristic: The inverter
accelerates the motor step by step up to the rated speed, measures the frictional torque und
writes the frictional torque into the intermediate points of the friction characteristic.
Precondition
The motor is permitted to accelerate up to the rated speed without endangering persons or
property.
306
Precontrol of the speed controller with frictional torque
Friction characteristic
Converter with the CU250S-2 Control Units
Operating Instructions, 04/2018, FW V4.7 SP10, A5E31759476B AG