Siemens SINAMICS S120 Function Manual page 167

V control
dc_max
Figure 4-20
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
dc_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 DC link voltage), the braking torque of the
drives with an active V
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
energy and, in turn, relieve the DC link.
V control without acceleration
dc_max
As for the normal V
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).
Drive functions
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Switching the V
dc_max
controller can be activated for one or more drives (p1240 = 1, 3). The V
controller is reduced by shifting the torque limit. These drives
dc_max
dc_max
control (p1240 = 1, 3), if the drive must not be accelerated by
dc_max
control on/off
controller is not active, feed energy back,
dc_max
controller can even be accelerated to absorb the braking
Servo control
4.15 Vdc control
dc_max
167