Vector Control Without Encoder - Siemens SINAMICS S150 NEMA Operating Instructions Manual

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Setpoint channel and closed-loop control

7.4 Vector speed/torque control with/without an encoder

Vector control without encoder

For sensorless vector control only (SLVC: Sensorless Vector Control), 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. 1 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

The changeover between closed-loop/open-loop operation is controlled on the basis of time

and frequency conditions (p1755, p1756, p1758 - only for induction motors). The system

does not wait for the time condition to elapse if the setpoint frequency at the ramp-function

generator input and the actual frequency are below p1755 x (1 - (p1756 / 100%))

simultaneously.

The transition from open-loop to closed-loop operation always takes place when the

changeover speed in p1755 is exceeded (characteristic

speed increase is set very slow and a changeover delay time > 0 is set in p1759, then the

transition takes place after the changeover delay time (characteristic

Changeover conditions

in the diagram below). If the

in the diagram

Operating Instructions, 12/2018, A5E36652151A

Enclosed Drives