Siemens SINAMICS S120 Function Manual page 105

feed energy back, the drives with an active Vdc_max controller can even be accelerated to
absorb the braking energy and, in turn, relieve the DC link.
Description of Vdc_max control without acceleration (p1240 = 7, 9)
As with p1240 = 1, 3, if the drive must not be accelerated by means of feedback from other
drives in the DC link, acceleration can be prevented by the setting p1240 = 7, 9. The
effective lower torque limit must not be greater than the torque limit offset (p1532).
Description of Vdc controller monitoring functions (p1240 = 4, 5, 6)
In the event of a power failure, the Line Module can no longer supply the DC link voltage,
particularly if the Motor Modules in the DC link line-up are drawing active power. To ensure
that the DC link voltage is not burdened with uncritical drives in the event of a power failure,
these drives can be switched off by a fault (F30003) with a parameterizable voltage
threshold (p1248). This is carried out by activating the Vdc_min monitoring function (p1240 =
5, 6).
In the event of a power failure, the DC link voltage can increase until it reaches the shutdown
threshold when drives are decelerated. To ensure that the DC link voltage is not burdened
with uncritical drives in the event of a power failure, these drives can be switched off by a
fault (F30002) with a parameterizable voltage threshold (p1244). This is carried out by
activating the Vdc_max monitoring function (p1240 = 4, 6).
Function diagrams (see SINAMICS S List Manual)
● 5650 Vdc_max controller and Vdc_min controller
Overview of key parameters (see SINAMICS S List Manual)
Adjustable parameters
● p1240 Vdc controller or Vdc monitoring configuration
● p1244 DC link voltage threshold, upper
● p1248 DC link voltage threshold, lower
● p1250 Vdc controller proportional gain
Display parameters
● r0056.14 Vdc_max controller active
● r0056.15 Vdc_min controller active
Drive Functions
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4
Servo control
3.14 Vdc control
105