Advanced commissioning
7.13 Overcurrent protection
SIMATIC ET 200pro FC-2 converter
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Operating Instructions, 04/2018, FW V4.7 SP10, A5E34257324B AF
7.13
Overcurrent protection
The vector control ensures that the motor current remains within the set torque limits.
If you use U/f control, you cannot set any torque limits. The U/f control prevents too high a
motor current by influencing the output frequency and the motor voltage (I-max controller).
I_max controller
Requirements
The torque of the motor must decrease at lower speeds, which is the case, for example, with
fans.
The load must not drive the motor continuously, e.g. when lowering hoisting gear.
Function
The I-max controller influences the output frequency and the motor voltage.
If the motor current reaches the current limit during acceleration, the I-max controller extends
the acceleration operation.
If the load of the motor is so large during stationary operation that the motor current reaches
the current limit, the I-max controller reduces the speed and the motor voltage until the motor
current is in the permissible range again.
If the motor current reaches the current limit during deceleration, the I-max controller extends
the deceleration operation.
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- 31 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 diagram 6300 in the List Manual.
