Function description
The converter has dierent U/f characteristics.
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① The voltage boost of the characteristic improves 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
Figure8-47 Characteristics of U/f control
With increasing speed or output frequency, the converter increases its output voltage U. The
maximum possible output voltage of the converter depends on the line voltage.
The converter can increase the output frequency even at the maximum output voltage. The
motor is then operated with eld weakening.
The value of the output voltage at the rated motor frequency p0310 also depends on the
following variables:
• Ratio between the converter size and the motor size
• Line voltage
Advanced commissioning
8.20Motor control
SINAMICS G120C Converters
Operating Instructions, 02/2023, FW V4.7 SP14, A5E34263257B AK 301