Siemens Sinamics S120 Function Manual page 149

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
Extended method: Closed-loop controlled operation down to 0 Hz
The actual rotor position can be continuously determined down to 0 Hz (standstill). With
Siemens 1FW4 and 1PH8 torque motors, the load can be maintained at standstill or, from
standstill, the motor can accelerate any load up to rated torque.
When the function is activated, at low speeds, additional noise can be heard, depending on
the motor design.
This method is suitable for motors with internal magnets.
Drive functions
Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
Zero point and starting in the open-loop controlled mode at low speeds
4.1 Sensorless vector control (SLVC)
Vector control
147