Siemens SINAMICS S120, Function Manual

Page: 240 / 1094

Vector control
5.9 Vdc control
Drive functions
240
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Vdc_min control
Figure 5-15 Switching V
dc_min
control on/off (kinetic buffering)
In the event of a power failure, V
dc_min
is activated when the V
dc_min
switch-on 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 V
dc_min
control is
deactivated again at 5% above the V
dc_min
switch-on level. The motor continues operating
normally.
If the power supply is not re-established, 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 re-established, a
fault is triggered (F07406), which can be parameterized as required (factory setting: OFF3).
The V
dc_min
controller can be activated for a drive. Other drives can participate in supporting
the DC link, by transferring to them a scaling of their speed setpoint from the controlling drive
via BICO interconnection.
Note
If it is expected that the line supply will return, you must make sure that the drive lineup is not
disconnected from the line supply. It could become disconnected, for example, if the line
contactor drops out. The line contactor must be supplied, e.g. from an uninterruptible power
supply (UPS).