Functions
7.7 Protection functions
Inverter with CU240B-2 and CU240E-2 Control Units
Operating Instructions, 07/2010, FW 4.3.2, A5E02299792B AA
179
Settings
NOTICE
The factory setting of the I
max
controller only needs to be changed in exceptional cases by
appropriately trained personnel.
Table 7- 19 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
P1345 Proportional gain of the I
max
controller for voltage reduction
P1346 Integral time of the I
max
controller for voltage 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.
r1344 Voltage output of I
max
controller
Shows the amount by which the I-max controller reduces the inverter output voltage.
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 electrical power flows back into the
inverter.
As a consequence, the DC link voltage in the inverter increases. The inverter can only
reduce the DC link voltage again if it has an energy recovery feature or it has a braking
resistor.
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".
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