8.20.3.4 Friction characteristic
Overview
In many applications, e.g. applications with geared motors or belt conveyors, the frictional
torque of the load is not negligible.
The converter provides the possibility of precontrolling the torque setpoint, bypassing the
speed controller. The precontrol reduces overshooting of the speed after speed changes.
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Figure8-53 Precontrol of the speed controller with frictional torque
The converter calculates the current frictional torque from a friction characteristic with 10
intermediate points.
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Figure8-54 Friction characteristic
The intermediate points of the friction characteristic are dened for positive speeds. In the
negative direction of rotation, the converter uses the intermediate points with a negative
sign.
Function description
Recording a friction characteristic
After quick commissioning, the converter 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 converter records the friction characteristic: The converter
accelerates the motor step by step up to the rated speed, measures the frictional torque and
writes the frictional torque into the intermediate points of the friction characteristic.
Requirement
The motor is permitted to accelerate up to the rated speed without endangering persons or
property.
Advanced commissioning
8.20Motor control
SINAMICS G120C Converters
316 Operating Instructions, 02/2023, FW V4.7 SP14, A5E34263257B AK
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