Siemens SINAMICS S120 Function Manual page 169

Note
If, in the closed-loop controlled mode, start from 0 Hz or reversing takes longer than 2 s, or
the time set in p1758 - then the system automatically changes over from closed-loop
controlled into open-loop controlled operation.
Note
Operation in encoderless torque control only makes sense if, in the speed range below the
changeover speed of the motor model (p1755), the setpoint torque is greater than the load
torque. The drive must be able to follow the setpoint and the associated setpoint speed
(p1499 , FBD 6030).
Passive loads
In the closed-loop controlled mode, for passive loads, induction motors can be operated
under steady-state conditions down to 0 Hz (standstill) without changing over into the open-
loop controlled mode.
Make the following settings for this:
1. p0500 = 2 (technological application = passive loads for encoderless control to f = 0).
2. Then set p0578 = 1 (calculate technology-dependent parameters).
As a consequence, the "Passive load" function is automatically activated.
Note
If p0500 is parameterized when commissioning the motor, the calculation is carried out
automatically via p0340 and p3900. p0578is is then set automatically.
Drive functions
Function Manual, (FH1), 01/2013, 6SL3097-4AB00-0BP3
The following parameters are then set automatically:
– p1574 = 2 V, separately-excited synchronous motors = 4 V
– p1750.2 = 1, closed-loop operation down to 0 Hz for passive loads
– p1802 = 4 SVM/FLB without overcontrol
– p1803 = 106% (factory setting)
4.1 Sensorless vector control (SLVC)
Vector control
167