8.21
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.
Changing the settings
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.
Parameter
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
Advanced commissioning
8.21 Overcurrent protection
Distributed converter for SIMOGEAR geared motors
Operating Instructions, 10/2020, FW V4.7 SP13, A5E31298649B AL
319