Siemens SINAMICS S120, Function Manual

Page: 239 / 1094

Vector control
5.9 Vdc control
Drive functions
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
239
5.9 Vdc control
The "Vdc control" function can be activated using the appropriate measures if an overvoltage
or undervoltage is present in the DC link.
● Overvoltage in the DC link
–
Typical cause
The drive is operating in regenerative mode and is supplying too much energy to the
DC link.
– Remedy
Reduce the regenerative torque to maintain the DC link voltage within permissible
limits. With the Vdc controller activated, the converter automatically partly extends the
ramp-down time of a drive if the shutdown supplies too much energy to the DC link.
● Undervoltage in the DC link
–
Typical cause
Failure of the supply voltage or supply for the DC link.
– Remedy
Specify a regenerative torque for the rotating drive to compensate the existing losses,
thereby stabilizing the voltage in the DC link (kinetic buffering).
Note
During operation of the Braking Module, the following must be observed:
•
You must set the threshold of the Braking Module below the V
dc_max
threshold.
• You must switch off the V
dc_max
controller.
Properties
● V
dc
control
– This comprises V
dc_max
control and V
dc_min
control (kinetic buffering), which are
independent of each other.
– Joint PI controller. The dynamic factor is used to set V
dc_min
and V
dc_max
control
independently of each other.
● V
dc_max
control
– This function can be used to control momentary regenerative load without shutdown
using "overvoltage in the DC link".
– V
dc_max
control is only recommended with a supply without active closed-loop control
for the DC link and without feedback.
● V
dc_min
control (kinetic buffering)
– With this function, the kinetic energy of the motor is used for buffering the DC link
voltage in the event of a momentary power failure, thereby delaying the drive.