Vector Control Without Encoder (Slvc); Three-Phase Induction Motor - Siemens SINAMICS S120 Function Manual

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Vector control without encoder (SLVC)

Function description

During operation via the "Sensorless vector control" function (SLVC), the position of the flux

and actual speed must be determined using the electric motor model. The motor model is

buffered by the incoming currents and voltages. At low frequencies (approx. 0 Hz), the motor

model cannot determine the speed with sufficient accuracy. For this reason, in this range, the

vector control can be changed over from closed-loop to open-loop control. When using passive

loads, additional limitations and constraints must be taken into consideration (see

Supplementary conditions for the operation of third-party motors).

The function can be used for the following motor types:

● Three-phase induction motors

● Permanent-magnet synchronous motors (PMSM)

● Synchronous reluctance motors (RESM)

The changeover between closed-loop/open-loop control is controlled by means of the time and

frequency conditions (p1755, p1756, p1758). If the setpoint frequency at the ramp-function

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

then the system does not wait for the time condition.

Setting the torque setpoint

In open-loop operation, the calculated actual speed value is the same as the setpoint value. For

static loads (e.g. for cranes) or during acceleration, you adapt the parameters p1610 (torque

Drive functions

Function Manual, 06/2019, 6SL3097-5AB00-0BP2

p1755 [1/min]

Changeover conditions for SLVC

6.2 Vector control without encoder (SLVC)

Vector control