Siemens SINAMICS S150 Operating Instructions Manual page 316

Functions, monitoring, and protective functions
9.3 Drive functions
Description of Vdc_min control (kinetic buffering)
Figure 9-4 Switching Vdc_min control on/off (kinetic buffering)
Note
Kinetic buffering must only be activated in conjunction with an external power supply.
When Vdc_min control is enabled with p1240 = 2.3 (p1280), it is activated if the power fails
when the Vdc_min switch-in level (r1246 (r1286)) is undershot. In general, the regenerative
power (braking energy) of the drive machine generated when the motor speed is reduced is
used to buffer the DC link voltage of the converter; in other words, when Vdc_min control is
active, the motor speed no longer follows the main setpoint and can be reduced to zero. The
SINAMICS system continues operating until the shutdown threshold of the DC link voltage is
undershot (see "Switching Vdc_min control on/off" <1>).
Note
All parameter specifications in parentheses refer to V/f control.
316
Drive converter cabinet units
Operating Instructions, 07/07, A5E00288214A