U/F Control - Siemens 6SL3845-2NN41-8AD2 Operating Instructions Manual

Operation
8.5 Functions
8.5.1.3

U/f control

As an alternative to vector control, a U/f control is available for induction motors. This technique
is only appropriate when there are no highly dynamic requirements, e.g. pumps and fan drives.
V/f control aims to maintain a constant flux Φ in the motor whereby the flux (Φ) is proportional
to the magnetization current (Iµ) and the ratio of voltage (V) to frequency (f).
Φ ~ Iµ ~ V/f
The torque (M) generated by the induction motors is, in turn, proportional to the vector product
(Φ x I) of the flux and current. The V/f characteristic is derived from these basic premises:
To generate as much torque as possible with a given current, the motor must function using the
greatest possible constant flux. To maintain a constant flux (Φ), therefore, the voltage must be
changed in proportion to the frequency f. The voltage change ensures that a constant
magnetization current Iµ flows.
Figure 8-4
Adjustable parameters
Parameter
p1300
Function diagrams
● 1590
● 1690
● 5060
● 6300
106
Operating areas and characteristic curves for the induction motor with drive supply
Setting
Open-loop/closed-loop operating mode / control type
Note
A simple rise in voltage can be achieved with parameter p6890. Refer to function diagram
6300.
SINAMICS SM150 6SL3845-2NN41-8AD2
Operating Instructions Rev.201910281310 EXAMPLE