General treatment method for inverter overcurrent fault

The output of the system generates a PWM voltage waveform. Once this signal passes through the windings, the resulting output current becomes approximately sinusoidal but lags behind the voltage by a phase angle, which is determined by the motor's power factor. The inverter's output current is monitored either via a precision resistor or a current transformer, and the obtained current signal is further processed by the CPU.

In order to safeguard the inverter, if the output current exceeds a predetermined threshold, the inverter will trigger an overcurrent fault and immediately halt the pulse output. This is a crucial and essential approach to prevent damage to the drive components. Unfortunately, once this fault occurs, it cannot be overridden.

There are numerous potential causes for an inverter overcurrent fault, and each situation must be analyzed based on its unique circumstances. Identifying the root cause and addressing it accordingly usually leads to a resolution. Begin by examining both the inverter side and the motor side after connecting the motor cable to the inverter and the motor itself.

A general approach to resolving inverter overcurrent faults includes:

Firstly, consider the inverter side:

Common causes of inverter overcurrent on this side include:

An excessively short acceleration time results in a higher demand for motor torque. Since torque is directly proportional to current, the current rises accordingly. To mitigate this, extend the acceleration time appropriately.

During the V/f control startup, if the voltage is boosted too high, it might lead to overcurrent issues. Adjust the voltage boost value downward to a more suitable level.

Improper PID parameters could result in excessive dynamic responses, causing overcurrent faults. Extend the filter time, reduce P, and adjust the I component accordingly.

Secondly, examine the motor side:

Potential causes of overcurrent on the motor side include:

A short circuit between the motor cable and ground: Poor cable insulation or damaged outer layers can cause this issue. Insulation testing using a megohmmeter can verify the cable's condition.

Motor stalling: In such cases, the inverter attempts to generate additional torque to get the motor moving, which may lead to an overcurrent fault.

Lastly, address any hardware problems:

If the internal current detection mechanism within the inverter is malfunctioning or if there is an issue with the CPU processing mechanism, these cannot be resolved by adjusting settings and require physical repair. Additionally, if the inverter is mismatched with the motor's current specifications—such as using a small inverter with a large motor or having incorrect nameplate parameters—it could also lead to overcurrent faults.