Siemens SINAMICS S120 Function Manual page 117

Figure 4-2
Closed-loop operation up to approx. 1 Hz (settable via parameter p1755) and the ability to
start or reverse at 0 Hz directly in closed-loop operation (settable via parameter p1750)
result in the following benefits:
● No switchover required within closed-loop control (smooth operation, no dips in
● Steady-state speed-torque control is possible up to approx. 1 Hz.
Permanent-magnet synchronous motors (PEM) are always started and reversed in open-
loop operation. The changeover speeds are set to 10% or 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.
Drive Functions
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4
Start-up and passing through 0 Hz in closed-loop operation
frequency).
Note
When the motor is started or reversed in closed-loop control at 0 Hz, it is important to
take into account that a switchover is made from closed-loop to open-loop control
automatically if the system remains in the 0 Hz range for too long (> 2 s or > p1758).
4.1 Sensorless vector control (SLVC)
Vector control
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