Siemens Sinamics S110 Function Manual page 160

Drive functions
7.1 Servo control
setpoint. If the supply voltage cannot be restored, the power supply will fail once the kinetic
energy of the drive has been exhausted with an active Vdc_min controller.
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 would
need to have an uninterruptible power supply (UPS), for example.
Description of Vdc_min control without braking (p1240 = 8, 9)
As with p1240 = 2, 3, however, active motor braking can be prevented by a reduction in the
supply voltage. The effective upper torque limit must not be less than the torque limit offset
(p1532). The motor does not switch to regenerative mode and no longer draws any active
power from the DC link.
Description of Vdc_max control (p1240 = 1, 3)
Figure 7-22
In the event of a power failure, the voltage can increase until it reaches the shutdown
threshold when the drive is decelerated. The Vdc_max controller can be activated to prevent
the system from shutting down due to overvoltage. The Vdc_max controller is normally
activated for drives that have to decelerate/accelerate high levels of kinetic energy
themselves. When the overvoltage threshold in p1244 is reached (recommended setting: 50
V higher than the supply voltage), the braking torque of the drive with an active Vdc_max
controller is reduced by shifting the torque limit. In this way, the drive feeds back the same
amount of energy that is assimilated as a result of losses or consumers, thereby minimizing
the braking time.
160
Switching-in/switching-out the Vdc_max control
Function Manual, 10/2008, 6SL3097-4AB10-0BP0
Drive functions