Siemens 6SL3845-2NN41-8AD2 Operating Instructions Manual page 104

Operation
8.5 Functions
Vector control with encoder
Benefits of vector control with an encoder:
● The speed can be controlled right down to 0 Hz (standstill).
● Stable control response throughout the entire speed range.
● Allows a defined and/or variable torque for speeds below approx. 10% of the rated motor
● In comparison with speed control without an encoder, the dynamic response of drives with
Function diagrams
● 1590
● 1610
● 6010
● 6030
● 6040
● 6050
● 6060
● 6490
Vector control without an encoder
Vector control without an encoder is used with induction motors.
In vector control without an encoder, the position of the flux and actual speed must be
determined via the electric motor model. The model is buffered by the incoming currents and
voltages. At low frequencies (approx. 0 Hz), the model cannot determine the speed.
For this reason and due to uncertainties in the model parameters or inaccurate measurements,
the system is switched from closed-loop to open-loop operation in this range.
The switchover is governed by time and frequency conditions (p1755, p1756, and p1758). If the
setpoint frequency at the ramp-function generator input and the actual frequency are below
p1755 x p1756 simultaneously, the system does not wait for the time condition.
104
speed to be maintained.
an encoder is significantly increased. The reason is that the speed is measured directly and
used for the model formation of the current components.
SINAMICS SM150 6SL3845-2NN41-8AD2
Operating Instructions Rev.201910281310 EXAMPLE