Siemens SINAMICS S120 Function Manual page 130

Operating Modes
Vector control
Description of Vdc_min control
V
controller
dc
active
Fig. 3-35
In the event of a power failure, Vdc_min control is activated when the Vdc_min
switch-in level is undershot. This controls the DC link voltage and maintains it at a
constant level. The motor speed is reduced.
When the power supply is restored, the DC link voltage increases again and
Vdc_min control is deactivated at 5 % above the Vdc_min switch-in level. The mo-
tor continues operating normally.
If the power supply is not reestablished, the motor speed continues to drop. When
the threshold in p1257 is reached, this results in a response in accordance with
p1256.
Once the time threshold (p1255) has elapsed without the line voltage being rees-
tablished, a fault is triggered (F07406), which can be parameterized as required
(factory setting: OFF3).
Note
You must make sure that the converter is not disconnected from the power supply.
It could become disconnected, for example, if the line contactor drops out. The line
contactor should be equipped with an uninterruptible power supply (UPS), for
example.
3-130
Power loss
r1286
without KIB fault
F30003
0.00V
1
0
--{}--n
setp
1/min
T
echnical data for ANT D10
I
qsetp
motor
0 A
Switching Vdc_min control on/off (kinetic buffering)
Power restore
without power restore fault F7405
Power loss
regenerative mode
© Siemens AG, 2005. All rights reserved
SINAMICS S120 Function Manual, 06/05 Edition
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