Inverter Overcurrent Fault General Processing Method
The output side of the inverter is the PWM voltage waveform. After passing through the motor windings, the output current is approximately a sine wave and lags behind the voltage by a phase angle. This angle is determined by the power factor of the motor. The output current of the inverter is detected by a precision resistor or a current transformer, and the CPU processes the current signal.
To protect the inverter, the inverter will report an overcurrent fault when the output current is above a certain threshold. The frequency converter also immediately blocks the pulse output. This is an important and necessary way to protect the drive components from damage. This fault cannot be blocked.
Causes of inverter overcurrent faults are many and should be analyzed based on actual conditions. If you look for the root cause, then you can solve the problem.
The motor cable is connected to the frequency converter and the motor. Then perform the analysis separately from the inverter side and the motor side.
First, the influence from the inverter side
The common causes of inverter overcurrent on the inverter side are:
The acceleration time is too short: the motor torque required at this time is greater, and the torque is proportional to the current, so the current is also large. The acceleration time can be appropriately extended.
Boost function: If the voltage is raised too high during start-up during V/f control, overcurrent may also be caused. The voltage boost value can be reduced appropriately.
Incorrect PID parameters: Excessive dynamic response may cause overcurrent. The filter time should be extended by subtracting P plus I.
2, followed by the influence from the motor side
The common causes of overcurrent in the inverter on the motor side are:
The motor cable is short-circuited to the ground: The cable is poorly insulated and broken. Cable insulation can be tested with a rocker to confirm cable quality.
Motor stalled: At this time, the inverter will try to use more torque to rotate the motor, which may cause overcurrent faults.
3, the last is the hardware problem
If the internal current detection mechanism of the frequency converter is not working properly, or if the CPU processing mechanism has a problem, these are not parameters that can be solved and need to be repaired.
If the inverter and the motor current do not match, it may also cause an overcurrent fault. For example, a small inverter with a large motor, or incorrect nameplate parameters, may cause over-current faults.