Siemens SINAMICS S120 Function Manual page 171

Active loads
Active loads, which can reverse the drive, e.g. hoisting gear, must be started in the open-
loop speed control mode. In this case, bit p1750.6 must be set to 0 (open-loop controlled
operation when the motor is blocked). The static (steady state) torque setpoint p1610 must
be greater than the maximum occurring load torque.
Note
Loads that can drive the motor
For applications with high regenerative load torques at low speeds, p1750.7 can also be set
to 1. As a result, the speed changeover limits of the motor model are increased and a faster
changeover can be made into open-loop controlled operation.
Permanent-magnet synchronous motors
Permanent-magnet synchronous motors (PEM) are always started and reversed in the open-
loop controlled mode. The changeover speeds are set to 10% as well as 5% of the rated
motor speed. Changeover is not subject to any time condition (p1758 is not evaluated).
Prevailing load torques (motor or regenerative) are adapted in open-loop operation,
facilitating constant-torque crossover to closed-loop operation even under high static loads.
Whenever the pulses are enabled, the rotor position is identified.
Figure 4-4
Drive functions
Function Manual, (FH1), 01/2013, 6SL3097-4AB00-0BP3
Zero point and starting in the open-loop controlled mode at low speeds
4.1 Sensorless vector control (SLVC)
Vector control
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