Efficient Networks Siemens Sinamics S120 - Manual (Page 134)

Vector control
4.9 Vdc control
Drive Functions
134
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4
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 may automatically extend 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).
Properties
● Vdc control
– This comprises Vdc_max control and Vdc_min control (kinetic buffering), which are
independent of each other.
– Joint PI controller. The dynamic factor is used to set Vdc_min and Vdc_max control
independently of each other.
● Vdc_max control
– This function can be used to control momentary regenerative load without shutdown
using “overvoltage in the DC link“.
– Vdc_max control is only recommended with a supply without active closed-loop control
for the DC link and without feedback.
● Vdc_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.