Siemens SINAMICS S120 Function Manual page 145

Switchover between closed-loop/open-loop operation and operation with/without encoder
Operation without an encoder is activated using parameter setting p1300 = 20. If p1300 = 20
or p1404 = 0, operation without an encoder is active across the entire speed range. If the
speed value is less than the changeover speed p1755, the motor is operated in accordance
with the current/frequency.
During operation with an encoder, a switchover can be made to operation without an
encoder when the speed threshold p1404 is exceeded. If p1404 > 0 and p1404 < p1755, a
switchover is not made to operation without an encoder until the speed exceeds p1755.
To prevent encoder evaluation alarms in encoderless operation, set p1402.1 = 1 to park the
encoder evaluation. Reading-in the motor temperature via the encoder evaluation remains
active.
Operation without an encoder is displayed in parameter r1407.1.
Figure 4-16
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.
Drive functions
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Area switchover
Servo control
4.12 Encoderless operation
145