Siemens MICROMASTER 440 Operating Instructions Manual page 174

3 Functions
For Vector control without speed actual value encoder MICROMASTER 440 has, in
the low frequency range, the following outstanding features with respect to other
AC drive inverters:
Closed-loop controlled operation down to ≈ 1 Hz
Can start in the closed-loop controlled mode (immediately after the drive has
been energized)
The low frequency range (0 Hz) is passed-through in closed-loop controlled
operation
P1755
Fig. 3-78
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):
No changeover operation is required within the closed-loop control
(smooth behavior – no frequency dips)
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.
174
Start
f
Closed loop
Open loop
Starting and passing-through 0 Hz in closed-loop controlled operation
f
Closed loop
P1755
t
P1755
MICROMASTER 440
Issue 10/03
Zero crossing
Open loop
t
Operating Instructions
6SE6400-5AW00-0BP0