Siemens SINAMICS G120 CU230P-2, Operating Instructions Manual, Page: 218 / 346

Functions
7.7 Protection functions
Frequency inverters with Control Units CU230P-2 HVAC, CU230P-2 DP, CU230P-2 CAN
216
Operating Instructions, 01/2011, FW 4.4, A5E02430659B AD
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 it is shut down due to overcurrent.
Table 7- 30 I
max
controller parameters
Parameter Description
P0305
Rated motor current
P0640 Motor current limit
P1340 Proportional gain of the I
max
controller for speed reduction
P1341 Integral time of the I
max
controller for speed reduction
r0056.13 Status: I
max
controller active
r1343 Speed output of I
max
controller
Shows the amount to which the I-max controller reduces the speed.
For more information about this function, see function diagram 1690 in the List Manual.
7.7.5 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 electric power flows back into the
inverter and causes V
DC
in the inverter to increase.
Above a critical DC link voltage both the inverter as well as 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
The V
DCmax
controller prevents – as far as the application permits – the DC link voltage from
reaching critical levels.
The V
DCmax
controller is not suitable for applications in which the motor is permanently in the
regenerative mode, e.g. in hoisting gear or when large flywheel masses are braked. Further
information on inverter braking methods can be found in Section Braking functions of the
converter (Page 225).