Siemens SINAMICS S120 Function Manual page 310

V/f control (vector control)
6.5 Vdc control
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
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
parameterization, the controllers can mutually influence one another negatively. The drives
can become unstable, individual drives can unintentionally accelerate.
Remedial measures:
● activate the V
– Vector control: p1240 = 1 (factory setting)
– Servo control: p1240 = 1
– V/f control: p1280 = 1 (factory setting)
● Inhibit V
– Vector control: p1240 = 0
– Servo control: p1240 = 0 (factory setting)
– V/f control: p1280 = 0
● Activate the V
– Vector control: p1240 = 4 or 6
– Servo control: p1240 = 4 or 6
– V/f control: p1280 = 4 or 6
Unexpected motion of individual drives
If several Motor Modules are supplied from one infeed unit, then if the V
incorrectly parameterized, individual drives can accelerate in an uncontrolled fashion -
which can lead to death or severe injury.
• Only activate the V
• Inhibit this function for all other Motor Modules, or set this function to monitoring only.
310
control is active for several Motor Modules, then for an unfavorable
dc_max
control:
dc_max
control:
dc_max
monitoring
dc_max
WARNING
dc_max
moment of inertia.
control for the Motor Module whose drive has the highest
control may only be
dc_max
dc_max
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
control is
Drive functions