Siemens SINAMICS G220 - U;F Control

14.10.4 U/f control
14.10.4.1 U/f control
Overview
The U/f control is an open-loop speed control in which the converter sets the output voltage
using a U/f characteristic. The U/f control is su󹪟cient for many simple applications.
Description of function
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In the "Flux current control (FCC)" variant of U/f control, the converter controls the motor current
(starting current) at low speeds.
Figure14-104 Simpli󹪝ed representation of U/f control
The U/f control has the following properties:
• The converter sets the output voltage on the basis of a U/f characteristic.
• The output frequency results largely from the speed setpoint and the number of pole pairs
of the motor.
• The slip compensation corrects the output frequency depending on the load and thus
increases the speed accuracy.
• Because the control loop is eliminated, the U/f control is stable in all cases.
• In applications with higher speed accuracy requirements, a load-dependent voltage boost
can be selected (󹪞ux current control, FCC)
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 depends, among other
things, on the following variables:
• Ratio of converter size to motor size
• Line voltage
Functions
14.10Closed-loop drive control
SINAMICS G220 converter
Operating Instructions, 04/2024, FW V6.2, A5E51781573B AB 493