Siemens SINAMICS S120 - Page 241

Vector control
5.9 Vdc control
Drive functions
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
241
Vdc_max control
Figure 5-16 Switching the V
dc_max
control on/off
The switch-on level for V
dc_max
-control (r1242) is calculated as follows:
● When the function for automatically detecting the switch-on level is switched off (p1254 =
0)
r1242 = 1.15 x p0210 (device connection voltage, DC link)
● When the function for automatically detecting the switch-on level is switched on (p1254 =
1)
r1242 = V
dc_max
- 50 V (V
dc_max
: Overvoltage threshold of the Motor Module)
If several Motor Modules are supplied from a non-regenerative infeed unit (e.g. a Basic Line
Module), or for power failure or overload (for SLM/ALM), the V
dc_max
control may only be
activated for a Motor Module whose drive should have a high moment of inertia.
For the other Motor Modules this function must be disabled or monitoring must be set.
If the V
dc_max
control is active for several Motor Modules, then for an unfavorable
parameterization, the controllers can mutually influence one another negatively. The drives
can become unstable, individual drives can unintentionally accelerate.