Siemens SINAMICS S150 NEMA, Руководство по эксплуатации

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Setpoint channel and closed-loop control
7.4 Vector speed/torque control with/without an encoder
Enclosed Drives
458
Operating Instructions, 12/2018, A5E36652151A
7.4.1 Vector control without encoder
Description
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
range.
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
①
in the diagram below). If the
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
②
in the diagram
below).
Figure 7-11 Changeover conditions