Siemens SINAMICS S120 Function Manual page 141

Figure 5-17
Note
In closed-loop control operating mode "Speed controller without encoder", a rotor position
encoder is not required. Temperature evaluation remains active, even when the encoder is
parked. This state can be identified at parameter r0458.26 = 1. When parameter r0458.26 = 0,
temperature sensing is also deactivated.
Series reactor
When high-speed special motors are used, or other low leakage induction motors, a series
reactor may be required to ensure stable operation of the current controller.
The series reactor can be integrated via p0353.
Commission and optimizing the function
Proceed as follows to start and optimize the function:
1. Estimate the motor current p1612 on the basis of the mechanical conditions (I = M/kt).
2. For synchronous motors with high overload setting (p0640 significantly higher than p0305),
it may be necessary to reduce the current limiting in encoderless operation (p0642).
3. For a third-party motor, carry out the stationary measurement - and if possible - also the
rotating measurement and accept the determined data (see Chapter "Motor data
identification (Page 142)"). Check the current controller setting.
Drive functions
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
Area switchover
Servo control
5.14 Encoderless operation
139