Vdc Control - Siemens Sinamics S110 Function Manual

7.1.14

Vdc control

Description
Vdc control can be activated if overvoltage or undervoltage is present in the supply voltage.
This prevents a fault from occurring due to the supply voltage and ensures that the drive is
always ready to use.
This function is activated by means of the configuration parameter (p1240). It can be
activated if an overvoltage or undervoltage is present. The torque limit of the motor at which
the Vdc controller is active can be affected if discrepancies in the supply voltage are
significant enough. The motor may no longer be able to maintain its setpoint speed or the
acceleration/braking phases could be prolonged.
The Vdc controller is an automatic P controller that influences the torque limits. It only
intervenes when the supply voltage approaches the "upper threshold" (p1244) or "lower
threshold" (p1248) and the corresponding controller is activated via the configuration
parameter (p1240).
An application for the Vdc controller is, for example, as a safety measure in the event of a
power failure (Vdc_min and Vdc_max controller).
Description of Vdc_min control (p1240 = 2, 3)
Figure 7-21
In the event of a power failure, the Power Module will no longer be able to maintain the
supply voltage, in particular if the motor is drawing active power. To maintain the supply
voltage in the event of a power failure (e.g. for a controlled emergency retraction), the
Vdc_min controller can be activated for the drive. If the voltage threshold set in p1248 is
undershot, this drive will be decelerated so that its kinetic energy can be used to maintain
the supply voltage. The threshold should be considerably higher than the trip threshold of the
motor (recommendation: 50 V below the supply voltage). When the power supply is restored,
the Vdc controller is automatically deactivated and the drive will ramp back up to the speed
Drive functions
Function Manual, 10/2008, 6SL3097-4AB10-0BP0
Switching Vdc_min control on/off (kinetic buffering)
Drive functions
7.1 Servo control
159