7.20.2.1 Characteristics of U/f control
The converter has dierent U/f characteristics.
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① The voltage boost of the characteristic optimizes the speed control at low speeds
② With the ux current control (FCC), the converter compensates for the voltage drop in the stator
resistor of the motor
The converter increases its output voltage to the maximum possible output voltage. The
maximum possible output voltage of the converter depends on the line voltage.
When the maximum output voltage is reached, the converter only increases the output
frequency. At this point, the motor enters the eld weakening range: At constant torque, the
slip decreases quadratically as the speed increases.
The value of the output voltage at the rated motor frequency also depends on the following
variables:
• Ratio between the converter size and the motor size
• Line voltage
Advanced commissioning
7.20Motor control
SINAMICS G115D Wall Mounted distributed drive
Operating Instructions, 07/2023, FW V4.7 SP14, A5E52808211A AA 285
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