Siemens SINAMICS SM150 - U;F Control

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.
I
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0
Q
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Q
I
Q
I
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83
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Figure 8-4 Operating areas and characteristic curves for the induction motor with drive supply
Adjustable parameters
Parameter Setting
p1300 Open-loop/closed-loop operating mode / control type
Function diagrams
● 1590
● 1690
● 5060
● 6300
Note
A simple rise in voltage can be achieved with parameter p6890. Refer to function diagram
6300.
Operation
8.5 Functions
SINAMICS SM150 6SL3845-2NN41-8AD2
106 Operating Instructions Rev.201910281310 EXAMPLE