Siemens SINAMICS S120 Function Manual page 134

Servo control
5.12 U/f control
Note
Restricted applications for U/f control
U/f control must only be used as a diagnostic function (e.g. check of the motor encoder
function). In order to obtain a pure diagnostic mode without any influence on actual values, the
resonance damping must be deactivated (p1338 = 0).
The activated U/f control blocks all other settings, for example current controller or speed
controller.
Structure of U/f control
The following figure shows a schematic of the structure of a U/f control:
Figure 5-14
U/f characteristic
The speed setpoint is converted to the frequency specification taking into account the number
of pole pairs. The synchronous frequency associated with the speed setpoint is output (no slip
compensation).
The following figure shows the U/f characteristic in schematic form:
Figure 5-15
132
Structure of U/f control
U/f characteristic
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
Drive functions