1. Overload fault
For overload faults, the first step should be to check if the motor is overheating. If the motor temperature rise is not high, first check if the inverter's thermal protection function is set appropriately. If the inverter has a margin, the preset value should be relaxed; if the inverter's allowable current has no margin, it indicates that the inverter selection is inappropriate, and the inverter capacity should be increased or the inverter replaced. Secondly, check if the power supply voltage and the three-phase voltage on the motor side are balanced. If the voltage at the inverter output is balanced, the problem lies in the wiring between the inverter and the motor. Finally, check for malfunctions. Under light load or no-load conditions, use an ammeter to measure the inverter's output current and compare it with the operating current value displayed on the screen. Check if there is a large error between the displayed and actual values; if so, the tripping is a malfunction.
2. Overheating fault
Causes of inverter overheating include: excessively high ambient temperature, poor inverter ventilation, fan jamming or damage, and excessive load. The corrective measures include checking the inverter's base plate for heat dissipation, and ensuring the inverter's own air ducts or the control cabinet's air ducts are not blocked. Regular maintenance of the inverter should be performed to remove debris from the air ducts and maintain proper ventilation.
3. Ground short circuit fault
The main causes of inverter ground fault tripping include: damaged motor insulation; damaged cable insulation; internal short circuit in the inverter; and several motors connected in parallel, resulting in a large ground leakage current at the inverter output. Additionally, cables have a certain distributed capacitance to ground. The magnitude of this capacitive current depends on factors such as cable length and insulation material; the longer the cable, the larger the capacitive current. Excessive cable length leads to a large capacitive current to ground, which can cause the inverter to trip due to a ground fault. To address this issue, a reactor can be connected in series between the inverter output and the motor.
4. Overcurrent fault
Overcurrent faults can generally be divided into acceleration, deceleration, and constant speed overcurrent. The main causes include too short starting acceleration time, sudden increase in load, short circuit of inverter output, uneven load distribution, mismatch between inverter and motor capacity, damage to internal rectifier or inverter side components, power supply phase loss, output disconnection, internal motor faults, and grounding faults.
For overcurrent faults, the troubleshooting method is as follows: When checking the fault, the load should be disconnected first to check the frequency converter. If the overcurrent fault still exists after disconnecting the load, it indicates that the internal components of the frequency converter are faulty and further inspection and repair are required.
To address these faults, the following measures can be taken: extend the acceleration time, design load distribution, inspect the lines, prevent interference and mechanical vibration, and reduce sudden load changes.
5. Overvoltage fault
Inverter overvoltage fault refers to the inverter tripping due to overvoltage when the DC bus voltage of the unit exceeds the limit. The main causes of unit overvoltage faults are: firstly, the high-voltage power supply on the input side exceeds the maximum allowable value; secondly, overvoltage tripping of the inverter occurs during deceleration. Inverter overvoltage faults include overvoltage when the compensation capacitor is connected, lightning overvoltage, overvoltage due to excessively short braking or deceleration time, and power supply overvoltage.
After a fault occurs, first check whether the input power supply voltage is stable, and check whether the motor starts while idling or is being driven by external force. Assuming the input power supply voltage is stable, add an absorption device to the power input side to reduce overvoltage factors. For situations where there is a possibility of impulse overvoltage, lightning-induced overvoltage, or overvoltage generated when the compensation capacitor is closed or opened, methods such as connecting a surge absorption device in parallel or a series reactor on the input side can be used to address these issues.
Overvoltage faults usually occur during shutdown and are related to intermediate circuits and braking components. The main causes are damage to the braking resistor or excessively short deceleration time. Therefore, the solution is to increase the deceleration time parameter or increase the braking resistor (braking unit).
6. Undervoltage fault
Undervoltage fault in a frequency converter refers to a voltage that is too low in the main circuit, such as below 180V for 220V series and below 300V for 380V series. This is generally caused by a phase loss in the power supply, too many frequency converters operating or starting simultaneously, damage to the thyristor in the current-limiting resistor or short-circuit current-limiting resistor in the inverter's internal DC circuit, or interference from external sources or between frequency converters. The corrective measures include checking the inverter's input section, verifying the circuit breaker or contactor contacts for good contact, checking for excessive contact resistance, verifying the transformer output voltage is normal, minimizing the number of frequency converters starting or operating simultaneously, and enhancing the inverter's anti-interference capabilities.
