Siemens SINAMICS S120 Function Manual page 171

V control
dc_max
Figure 5-27
With Infeed Modules without feedback or in the event of a power failure, the DC link voltage can
increase until it reaches the shutdown threshold when drives in the DC link line-up are
decelerated. To prevent the system from shutting down due to a DC link overvoltage, the V
controller can be activated for one or more drives (p1240 = 1, 3). The V
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 DC link voltage), the braking torque of the drives with an active V
is reduced by shifting the torque limit. These drives feed back exactly the same amount of
energy, that is drawn as a result of losses or loads in the DC link. This function minimizes the
braking time.
Note
If other drives in the drive line-up, where the V
the drives with an active V
and, in turn, relieve the DC link.
V control without acceleration
dc_max
As for the normal V
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).
V monitoring
dc controller
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 loaded with uncritical drives in the event of a power failure, these
drives can be switched off with fault F7403 (Drive: lower DC link voltage threshold reached) with
a parameterizable threshold in p1248. This is carried out by activating the V
function (p1240 = 5, 6).
Drive functions
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
Switching the V control on/off
dc_max
controller can even be accelerated to absorb the braking energy
dc_max
control (p1240 = 1, 3), if the drive must not be accelerated by means
dc_max
controller is not active, feed energy back,
dc_max
Servo control
5.17 Vdc control
dc_max
controller is
dc_max
controller
dc_max
monitoring
dc_min
169