Siemens SINAMICS G150 Operating Instructions Manual page 389

NOTICE
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).
Closed-loop operation down to standstill for passive loads
By restricting to a passive load at the starting point, it is possible to maintain stationary
closed-loop operation down to zero frequency (standstill) without having to change over to
open-loop operation.
Parameter p1750.2 must be set to 1.
Closed-loop control without changeover is restricted to applications with passive load:
These include applications in which the load cannot produce a regenerative torque on
startup and the motor comes to a standstill when pulses are inhibited; for example, moments
of inertia, brakes, pumps, fans, centrifuges, extruders, ....
Standstill of any duration is possible without holding current, only the motor magnetization
current is impressed.
Steady-state regenerative operation at a frequency close to 0 Hz is not possible.
It is also possible to select sensorless control for passive loads during commissioning by
setting p0500 = 2 (technology application = passive loads (for sensorless control down to f =
0)).
This function is activated automatically if quick commissioning is exited with p3900 > 0, or if
automatic calculation is called (p0340 = 1, 3, 5 or p0578 = 1).
Blocking drives
If the load torque is higher than the torque limiting of the sensorless vector control, the drive
is braked to zero speed (standstill). In order that the open-loop controlled mode is not
selected after the time p1758, p1750.6 can be set to 1. Under certain circumstances p2177
(Motor blocked delay time) must be increased.
NOTICE
Exception for reversing drives
It is not permissible to use this setting if the load can force the drive to reverse.
Converter cabinet units
Operating Instructions, 03/2012, A5E03263466A
Setpoint channel and closed-loop control
7.4 Vector speed/torque control with/without encoder
387