With the rapid advancement of power and electronic technologies, as well as the modernization of industrial infrastructure, more and more users in the control field are demanding higher performance from electrical equipment. The introduction and widespread use of frequency converters have simplified complex control systems, making production processes more efficient, faster, and precise. However, like any other control device, inverters are not immune to faults. To minimize downtime and losses, it is crucial to quickly identify the type and cause of the fault. Today, Yikong Jun has compiled a detailed guide on common issues that occur during the daily operation of inverters, along with practical inspection methods, hoping to assist engineers and technicians in troubleshooting effectively.
1. **Overcurrent Fault**
Overcurrent faults can generally be categorized into three types: overcurrent during acceleration, deceleration, and constant speed. Common causes include too short acceleration time, sudden load increase, inverter output short circuits, uneven load distribution, mismatch between inverter and motor capacity, internal component damage on the rectifier or inverter side, power phase loss, output disconnection, motor internal faults, and ground faults.
To address overcurrent faults, first disconnect the load and check the inverter. If the overload persists, it likely indicates an internal component failure, requiring further inspection. Measures such as extending acceleration time, balancing the load, checking wiring, reducing interference, and avoiding sudden load changes can help prevent future issues.
2. **Overvoltage Fault**
An overvoltage fault occurs when the DC bus voltage exceeds its allowable limit. Causes may include high input voltage, overvoltage during deceleration, lightning surges, excessive braking time, or overvoltage caused by capacitor switching.
Upon encountering an overvoltage fault, first verify the stability of the input voltage, check if the motor is rotating freely, and ensure no external forces are dragging it. If the input voltage is stable, consider adding an absorption device on the input side to reduce overvoltage. For lightning-induced or capacitor-related overvoltage, installing a parallel surge absorber or series reactor can be effective. Overvoltage often occurs during shutdown, related to the intermediate circuit and braking system. A damaged brake resistor or too short deceleration time may be the root cause, so increasing the deceleration time or adding a braking resistor is recommended.
3. **Undervoltage Fault**
An undervoltage fault occurs when the main circuit voltage drops below the required level, such as 180V for a 220V system or 300V for a 380V system. This can result from phase loss, simultaneous operation of multiple inverters, damaged current-limiting resistors or thyristors, or external interference.
To resolve this issue, check the inverter's input section, ensure the power supply is connected properly, and confirm that contactor contacts are good. Also, verify that the transformer’s output voltage is normal and reduce the number of inverters operating simultaneously. Enhancing the inverter’s anti-interference capability can also help prevent such faults.
4. **Overload Fault**
An overload fault occurs when the motor runs but the current exceeds the rated value. This is typically due to excessive mechanical load or possible malfunctions.
When dealing with overload faults, first check if the motor is overheating. If the motor temperature is normal, verify whether the inverter’s thermal protection settings are correctly configured. If there is still margin, adjust the settings accordingly. If not, consider upgrading the inverter’s capacity. Additionally, check the supply voltage and three-phase balance on the motor side. If the inverter output is balanced, the issue may lie in the wiring. Finally, test for malfunctions by measuring the actual output current and comparing it with the displayed value.
5. **Overheat Fault**
Overheat faults can occur due to high ambient temperatures, poor ventilation, fan failure, or excessive load.
To address this, inspect the inverter’s heat dissipation, ensure the air ducts are clear, and regularly clean the vents. Maintaining proper airflow and ensuring the cooling system is functioning correctly are essential to preventing overheating.
6. **Ground Short Circuit Fault**
A ground short circuit trip can be caused by damaged motor insulation, faulty cable insulation, internal inverter short circuits, or multiple motors connected in parallel leading to large ground leakage currents. The distributed capacitance of long cables can also contribute to ground leakage, especially with poor insulation materials.
To mitigate this, consider connecting a reactor in series with the motor on the inverter’s output side to reduce the capacitive current and prevent ground faults.
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