Siemens SINAMICS G120P, Руководство по эксплуатации

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Functions
7.6 Protection functions
Inverter cabinet units
Operating Instructions, 12/2014, A5E32923362A
369
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 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 the I-max controller
Shows the amount to which the I-max controller reduces the speed.
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
DC
in the inverter to increase.
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).