Siemens Sinamics S120 Function Manual page 227

2. Overvoltage in the DC link
Properties
● Vdc control
● Vdc_min control (kinetic buffering)
● Vdc_max control
Drive functions
Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
– 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).
– 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.
– This comprises Vdc_max control and Vdc_min control (kinetic buffering). These two
functions can be parameterized independently of one another and activated.
– There is a common PID controller. The dynamic factor is used to set Vdc_min and
Vdc_max control to a smoother or harder setting independently of each other.
– 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.
– 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.
U/f control (vector control)
5.4 Vdc control
225