Sensorless control for synchronous motor (SL-PSM)
The sensorless control for synchronous motors is based on a decoupled, separated control of the torque-producing current and the current aligned with the field. In contrast to the servo control, the actual speed value and rotor position are reconstructed via a motor model.
NOTICE
In case of this motor control type, an adjustable, constant current is injected in the lower speed range. If this current is higher than the rated motor current, the motor may heat up in the lower speed range. This effect increases if the motor is operated in the lower speed range for a longer period of time.
Possible consequences: Destruction of the motor by overheating
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Do not operate the motor for a longer period of time in the lower speed range.
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For detecting and monitoring the motor temperature, we recommend a temperature feedback via PTC thermistor or thermal contact. 
Motor temperature monitoring
Motor temperature monitoring Details
The motor model-based speed observer requires a rotating machine. Thus, as a matter of principle, the operational performance of the sensorless control for synchronous motors is divided into two ranges:
1.
Low speed range (|setpoint speed| < lower limit 0x2C11:001)
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In the range of low speeds, the speed of a synchronous motor cannot be observed. In this "Low speed range", controlled operation takes place: During the acceleration phase
, the current setpoints of 0x2C12:001 and 0x2C12:002 are added and injected into the motor.
, the current setpoints of 0x2C12:001 and 0x2C12:002 are added and injected into the motor.
2.
High speed range (|setpoint speed| > lower limit 0x2C11:001)
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In this range, the rotor flux position and the speed are reconstructed by means of observation. The control is executed in a field-oriented way. Only the current required for generating the necessary torque is injected.
Pole position identification (PLI)
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For controlling a permanent-magnet synchronous motor, the pole position - the angle between the motor phase U and the field axis of the rotor - must be known.
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If the drive is at a standstill, the "pole position identification (PLI)" function is immediately activated after the inverter is enabled. Synchronous motor: Pole position identification (PPI)
Synchronous motor: Pole position identification (PPI) Flying restart circuit
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A flying restart circuit for the synchronous motor up to speeds lower than half the rated speed is supported.
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If the flying restart circuit is to be used, set the start method "Flying restart circuit [2]" in 0x2838:001 (P203.01). Additional settings are not required for the flying restart circuit in the case of a sensorless control of a synchronous motor.
SL-PSM parameters
The parameters for this motor control type are calculated and set automatically while optimising the control loops.