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6.7.3
Encoderless vector control
6.7.3.1
Structure of vector control without encoder (sensorless)
Overview
The vector control comprises closed-loop current control and a higher-level closed-loop speed
control.
for induction motors
1)
Settings that are required
2)
Figure 6-76
Simplified function diagram for sensorless vector control with speed controller
Using the motor model, the converter calculates the following closed-loop control signals from
the measured phase currents and the output voltage:
● Current component I
● Current component I
● Speed actual value
The setpoint of the current component I
speeds above the rated speed, the converter reduces the flux setpoint along the field
weakening characteristic.
When the speed setpoint is increased, the speed controller responds with a higher setpoint for
current component I
setpoint by adding a higher slip frequency to the output frequency. The higher output frequency
also results in a higher motor slip, which is proportional to the accelerating torque. I
SINAMICS G120X converter
Operating Instructions, 06/2019, FW V1.01, A5E44751209B AC
q
q
(flux setpoint) is obtained from the motor data. For
d
(torque setpoint). The closed-loop control responds to a higher torque
q
Advanced commissioning
6.7 Motor control
and
q
391
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