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Advanced commissioning
6.8 Drive protection
6.8
Drive protection
6.8.1
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).
Requirement
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.
Parameter
The factory setting for proportional gain and the integral time of the I-max controller ensures
faultless operation in the vast majority of cases.
The factory setting of the I-max controller must only be changed in the following exceptional
cases:
● Speed or torque of the motor tend to cause vibrations upon reaching the current limit.
● The converter goes into the fault state with an overcurrent message.
Table 6-101 I-max controller parameters
Number
r0056.0 ... 13
p0305[M]
p0640[D]
p1340[D]
p1341[D]
r1343
404
Name
CO/BO: Status word, closed-loop control
Rated motor current
Current limit
I_max frequency controller proportional gain
I_max frequency controller integral time
CO: I_max controller frequency output
Operating Instructions, 06/2019, FW V1.01, A5E44751209B AC
Factory setting
-
0 Arms
0 Arms
0
0.300 s
- rpm
SINAMICS G120X converter
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