Siemens SINAMICS S120 Function Manual page 218

Vector control
6.2 Vector control without encoder (SLVC)
Note
Synchronous reluctance motors are considered to be synchronous motors
Generally, the data for "Synchronous motors" provided in the SINAMICS S120 Manuals also
applies to "Synchronous reluctance motors". Any deviating behavior/response of synchronous
reluctance motors is always explicitly specified.
Features
For the motor type RESM in the default configuration (without test signal), at low speeds the
system changes over into speed-controlled operation is also started in this way. The load
torque requirement expected must be known for open-loop speed controlled operation, and
can be parameterized using p1610 and p1611.
When reaching the voltage limit (depending on the load and speed), the motor flux is
appropriately reduced (field weakening). Depending on the torque demanded, the required
motor current increases up to the available current limit. If the speed is increased further, the
current must be reduced to below the available current limit in order to maintain the voltage limit.
In this range, the motor power available is therefore solely limited by the available voltage; for
synchronous reluctance motors, as a result of the saturation attributes, it is slightly below that
for induction motors.
Closed-loop controlled operation down to f = 0 Hz
Due to the magnetically anisotropic rotor, sensorless field-oriented operation can be continued
until standstill (f = 0 Hz) in the synchronous reluctance motor. A replacement of the field
orientation at low speed in an open-loop mode, as physically required with other machines, can
thus be omitted in the synchronous reluctance motor.
To determine the rotor position and speed from voltage and current, not only their large signal
levels are used. Additive small excitation pulses are superimposed on the driving fundamental
voltage and the resulting current changes, which are dependent on the rotor position, are
evaluated.
Functionally, the process permits a behavior that is completely equivalent to control operation
with speed-position sensor. For example, sensorless torque control can be used without
limiting the speed range. The achieved dynamics are only insignificantly reduced compared to
operation with sensor for the vast majority of vector applications.
Requirements
● Vector control
● Only Motor Modules in the "Booksize" format
● Valid license ("Advanced synchronous reluctance control")
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Function Manual, 06/2019, 6SL3097-5AB00-0BP2
Drive functions