Siemens SINAMICS S120 Function Manual page 138
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Servo control
3.14 Vdc control
Vdc_max control
Figure 3-17
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
Vdc_max controller can be activated for one or more drives (p1240 = 1, 3). The Vdc_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 Vdc_max controller is reduced by shifting the torque limit. These drives
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 Vdc_max controller is not active, feed energy
back, the drives with an active Vdc_max controller can even be accelerated to absorb the
braking energy and, in turn, relieve the DC link.
Vdc_max control without acceleration
As for the normal Vdc_max control (p1240 = 1, 3), if the drive must not be accelerated by
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).
136
Switching-in/switching-out the Vdc_max control
Function Manual, (FH1), 01/2013, 6SL3097-4AB00-0BP3
Drive functions
- Quick Links:
- Active Infeed
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