Siemens SINAMICS S120 Function Manual page 124

Operating Modes
Vector control
f
p1755
Fig. 3-27
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 para-
meter p1750) result in the following benefits:
S No switchover required within closed-loop control (smooth operation, no dips in
frequency).
S Steady-state speed-torque control up to approx. 1 Hz.
Note
When the motor is started or reversed in closed-loop operation at 0 Hz, it is
important to take into account that the system switches from closed-loop to
open-loop control automatically if the system remains in the 0 Hz range for too
long (> 2 s or > p1758).
Function diagram overview (refer to the List Manual)
S 6730
S 6731
3-124
Start
Closed loop
Open loop
Start-up and passing through 0 Hz in closed-loop operation
Interface with Motor Module for induction motor (p0300 = 1)
Interface to the Motor Module (PEM, p0300 = 2)
f
Closed loop
p1755
t
p1755
© Siemens AG 2006 All Rights Reserved
SINAMICS S120 Function Manual, 03/2006 Edition
Zero crossover
Open loop
t