Siemens Sinamics S120 Function Manual page 146

Vector control
4.1 Sensorless vector control (SLVC)
● Reversing without the need to change into the open-loop controlled mode is possible, if
● In the closed-loop torque controlled mode, at low speeds, the system always switches
Figure 4-2
Closed-loop operation to approx. 0 Hz (can be set using parameter p1755) and the
possibility to start or reverse at 0 Hz directly in closed-loop operation (can be set using
parameter p1750) result in the following benefits:
● No switchover operation required within closed-loop control (bumpless behavior, no
● Closed-loop speed control without encoder down to and including 0 Hz
● Passive loads down to a frequency of 0 Hz
● Steady-state closed-loop speed control down to approx. 0 Hz possible
● Higher dynamic performance when compared to open-loop controlled operation
Note
If, in the closed-loop controlled mode, start from 0 Hz or reversing takes longer than 2 s, or
the time set in p1758 - then the system automatically switches over from closed-loop
controlled into open-loop controlled operation.
NOTICE
Operation in encoderless torque control only makes sense if, in the speed range below the
changeover speed of the motor model (p1755), the setpoint torque is greater than the load
torque. The drive must be able to follow the setpoint and the associated setpoint speed
(p1499 , FBD 6030).
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the range of the changeover speed p1755 is passed through in a shorter time than the
changeover delay time set in p1758, and the speed setpoint in front of the ramp-function
generator lies outside the open-loop controlled speed range of p1755.
over into the open-loop controlled mode.
Zero crossover and when induction motors start in closed-loop or open-loop controlled
operation
frequency dips, no discontinuities in the torque).
Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
Drive functions