6.7 Drive protection
6.7.1 Overcurrent protection
Overview
The U/f control prevents too high a motor current by influencing the output frequency and the
motor voltage (I-max controller).
Precondition
You have selected U/f control.
The application must allow the motor torque to decrease at a lower speed.
Function description
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 motor load is so high during steady-state operation that the motor current reaches the
current limit, then the I-max controller reduces the speed and the motor voltage until the motor
current returns to the permissible range again.
If the motor current reaches the current limit during deceleration, the I-max controller extends
the deceleration operation.
Parameters
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 6-66 I-max controller parameters
Number Name Factory setting
r0056.0 … 13 CO/BO: Status word, closed-loop control -
p0305[M] Rated motor current 0 Arms
p0640[D] Current limit 0 Arms
p1340[D] I_max frequency controller proportional gain 0
p1341[D] I_max frequency controller integral time 0.300 s
r1343 CO: I_max controller frequency output - rpm
You will find more information about this function in function diagram 6300 and in the parameter
list.
Advanced commissioning
6.7 Drive protection
SINAMICS G120XA converter
Operating Instructions, 03/2019, FW V1.0, A5E44751205B AB 301
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