3  Functions  Issue 10/06 
  MICROMASTER 440      Operating Instructions 
246  6SE6400-5AW00-0BP0 
¾  Closed-loop controlled operation down to ≈ 1 Hz 
¾  Can start in the closed-loop controlled mode (immediately after the drive has 
been energized) 
¾  The low frequency range (0 Hz) is passed-through in closed-loop controlled 
operation 
f
t
P1755
Closed loop
Open loop
Start
f
t
Closed loop
Open loop
Zero crossing
P1755
P1755
 
Fig. 3-103  Starting and passing-through 0 Hz in closed-loop controlled operation   
The following advantages are obtained as a result of closed-loop controlled 
operation down to approx. 1 Hz (this can be selected using parameter P1755) as 
well as also the possibility to immediately start closed-loop controlled at 0 Hz or to 
reverse closed-loop controlled (this can be set using parameter P1750): 
¾  No changeover operation is required within the closed-loop control  
(smooth behavior – no frequency dips) 
¾  Continuous closed-loop speed-torque control is possible down to approx. 1 Hz. 
NOTE 
For closed-loop controlled reversing or closed-loop controlled starting from 0 Hz it 
must be taken into account that when staying too long (> 2 s or > P1758) in the 
range around 0 Hz, that the closed-loop control automatically changes-over from 
closed-loop into the open-loop controlled mode.