Table of Contents
Advertisement
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 sufficient for many simple applications.
Description of function
1)
Figure 14-104
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 (flux 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 field 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
SINAMICS G220 converter
Operating Instructions, 04/2024, FW V6.2, A5E51781573B AB
In the "Flux current control (FCC)" variant of U/f control, the converter controls the motor current
(starting current) at low speeds.
Simplified representation of U/f control
Functions
14.10 Closed-loop drive control
493
Advertisement
Table of Contents
