Limiting The Maximum Dc Link Voltage - Siemens Sinamics G120P Operating Instructions Manual

Settings
You only have to change the factory settings of the I-max controller if the drive tends to
oscillate when it reaches the current limit or if it is shut down due to overcurrent.
Table 7- 24
Parameter
p0305
p0640
p1340
p1341
r0056.13
r1343
For more information about this function, see function block diagrams 1690 and 6714 in the
List Manual.
7.6.5

Limiting the maximum DC link voltage

How does the motor generate overvoltage?
An induction motor operates as a generator if it is driven by the connected load. A generator
converts mechanical power into electrical power. The electrical power flows back into the
inverter and causes V
Above a critical DC-link voltage both the inverter and the motor will be damaged. Before the
voltage can reach critical levels, however, the inverter switches the motor off with the fault
message "DC-link overvoltage".
Protecting the motor and inverter against overvoltage
To the extent the application permits, the Vdc_max control prevents the DC-link voltage from
reaching critical levels. The Vdc_max control increases the ramp-down time of the motor
during braking, so that the motor feeds back only as little power to the inverter as is covered
by the losses in the inverter.
The Vdc_max control is not suitable for applications where the motor is continuously in the
generator mode. This includes, for example, cranes or applications involving braking large
moments of inertia. Further information on inverter braking methods can be found in Section
Braking functions of the converter (Page 380).
Inverter cabinet units
Operating Instructions, 12/2014, A5E32923362A
I-max controller parameters
Description
Rated motor current
Motor current limit
Proportional gain of the I-max controller for speed reduction
Integral time of the I-max controller for speed reduction
Status: I-max controller active
Speed output of the I-max controller
Shows the amount to which the I-max controller reduces the speed.
in the inverter to increase.
DC
Functions
7.6 Protection functions
369