Siemens SINAMICS S120 Function Manual page 138

Vector control
4.7 Torque control
The total of the two torque setpoints is limited in the same way as the speed control torque
setpoint. Above the maximum speed (p1082), a speed limiting controller reduces the torque
limits in order to prevent the drive from accelerating any further.
True torque control (with self-adjusting speed) is only possible in closed-loop but not open-
loop control for sensorless vector control (SLVC). In open-loop control, the torque setpoint
adjusts the setpoint speed via a ramp-function generator (integration time ~ p1499 x p0341 x
p0342). For this reason, encoderless torque control at standstill is only suitable for
applications that require an accelerating torque but no load torque (e.g. traction drives). This
restriction does not apply to torque control with sensor.
OFF responses
● OFF1 and p1300 = 22, 23
● OFF1, p1501 = "1" signal and p1300 ≠ 22, 23
● OFF2
● OFF3
138
– Reaction as for OFF2
– No separate braking response; the braking response takes place by a drive that
specifies the torque.
– The pulses are suppressed when the brake application time (p1217) expires. Standstill
is detected when the actual speed value is less than the speed threshold (p1226) or
when the monitoring time (p1227) that started when speed setpoint ≤ speed threshold
(p1226) has expired.
– Switching on inhibited is activated.
– Immediate pulse suppression, the drive coasts to standstill.
– The motor brake (if parameterized) is closed immediately.
– Switching on inhibited is activated.
– Switch to speed-controlled operation
– n_set = 0 is input immediately to brake the drive along the OFF3 deceleration ramp
(p1135).
– When zero speed is detected, the motor brake (if parameterized) is closed.
– The pulses are suppressed when the motor brake application time (p1217) has
elapsed. Standstill is detected when the actual speed value is less than the speed
threshold (p1226) or when the monitoring time (p1227) that started when speed
setpoint ≤ speed threshold (p1226) has expired.
– Switching on inhibited is activated.
Function Manual, (FH1), 10/2008, 6SL3097-2AB00-0BP5
Drive functions