Inverte

As a core device in the field of industrial automation, the stable operation of an inverter directly affects the production process. The following is a detailed analysis of five major types of high-frequency faults (overcurrent, output phase loss, ground fault, overheating, and overvoltage) from four dimensions: fault codes, possible causes, on-site troubleshooting steps, and solutions, helping technicians quickly locate and resolve problems.

1. Overcurrent Fault (Fault Codes: E004, E005, E006)

Overcurrent fault is one of the most common fault types of inverters. It is necessary to first distinguish between “actual overcurrent” and “false overcurrent” before conducting targeted troubleshooting to avoid blind maintenance.

1.1 Possible Causes of Fault

Actual Overcurrent	Incorrect Parameter Settings	– Too short acceleration/deceleration time: The motor accelerates/decelerates rapidly in a short time, leading to a surge in current; – Improper parameters in VF control mode: Excessively high manual torque boost (resulting in excessive current at low frequencies) or mismatched VF curve with motor characteristics (e.g., using a light-load curve in a heavy-load scenario).
	Hardware and Selection Issues	– Undersized inverter: The actual load current exceeds the rated current of the inverter for a long time; – Output short circuit: Short circuit between output phases (e.g., phase wires touching due to cable damage) or output ground fault (cable insulation layer damaged and touching the cabinet).
	Load and Motor Problems	– Motor stalling: Mechanical load jamming (e.g., conveyor belt stuck, foreign objects blocking the pump body), causing the motor speed to drop sharply and current to rise drastically; – Motor damage: Short circuit in the motor winding or stuck bearing, leading to abnormal increase in operating current.
False Overcurrent	Faults in Sampling and Detection Circuits	– Hall element failure: The Hall sensor for current detection is damaged and cannot accurately collect current signals; – Poor contact of Hall terminal blocks: Loose or oxidized terminals, resulting in interruption or distortion of sampling signals; – Failure of the current sampling circuit on the drive board: Damage to components such as sampling resistors and operational amplifiers, making it impossible to process current signals normally.
	Connection and Module Faults	– Poor connection between the control board and drive board: Loose flat cables or oxidized pins, leading to abnormal transmission of control signals; – Poor contact of module drive wires: Loose drive signal wires of the IGBT module, causing misjudgment of current detection; – IGBT module failure and short circuit: Internal breakdown of the module, leading to abnormal output current and triggering overcurrent protection.
Interference Factors	External Strong Interference and Poor Grounding	– Strong interference sources such as contactors and relays on-site: Electromagnetic interference generated during startup and shutdown invades the current sampling circuit, causing signal misjudgment; – Poor inverter grounding: No independent grounding or excessive grounding resistance, making it impossible to effectively discharge interference signals and affecting the accuracy of current detection.

1.2 On-site Troubleshooting Steps

1. Preliminary Judgment of Hardware Status: Disconnect the inverter power supply, wait for the capacitors to discharge completely (about 5-10 minutes), and use a multimeter to measure the conductivity of the main circuit module (IGBT) to determine if the module is short-circuited (under normal circumstances, there should be no conduction between the upper and lower tubes of the same bridge arm; otherwise, the module is faulty).
2. Confirm Fault Recurrence Conditions: Record the working conditions (e.g., during startup, operation, shutdown) and load status (no-load/heavy load) when the fault occurs, and clarify whether the fault is triggered under specific conditions (e.g., fault reported every time acceleration reaches a certain frequency).
3. Distinguish Between Actual and False Overcurrent:
   • Check the inverter fault record: Read the “fault current value” and “fault frequency” at the time of the fault, and compare them with the rated motor current and rated inverter current to determine if they exceed the normal range;
   • Measure the output current in real time: Before the fault recurs, use a clamp ammeter to measure the current at the inverter output terminal. If the current actually exceeds the rated value, it is actual overcurrent; if the current is normal but a fault is reported, it is false overcurrent.
4. Troubleshooting for Actual Overcurrent:
   • Check parameters: Enter the inverter parameter interface to check whether parameters such as acceleration/deceleration time, torque boost, and VF curve match the motor and load characteristics (e.g., extend the acceleration/deceleration time and reduce the manual torque boost value in heavy-load scenarios);
   • Check the load and motor: Disconnect the motor cable, manually rotate the motor shaft to determine if it is stuck; use a megohmmeter to measure the insulation resistance of the motor winding to ground (should be ≥500MΩ under normal conditions), and use a multimeter to measure the inter-phase resistance of the winding (the three-phase resistance should be balanced, with a deviation ≤5%).
5. Troubleshooting for False Overcurrent:
   • No-load test: Disconnect the inverter output cable (disconnect the motor connection), power on the inverter and run it (gradually increase the frequency from 0). If the inverter still reports an overcurrent fault under no-load conditions, it indicates an internal hardware fault of the inverter (e.g., Hall, drive board, IGBT module);
   • Check the connection lines: Re-plug the flat cable between the control board and the drive board, and the terminals of the Hall sensor, and clean the oxidized pins; check whether the module drive wires are secure and free of damage.

1.3 Solutions

• Parameter Adjustment: Reset the acceleration/deceleration time according to the load type (extend to 10-30 seconds for heavy loads), optimize the VF curve (select the “constant torque curve” for heavy loads and the “decreasing torque curve” for light loads), and reduce the manual torque boost value (generally set to 0.5%-2%).
• Hardware Repair/Replacement:
  • Damaged Hall elements, sampling resistors, or operational amplifiers: Replace the corresponding components;
  • Short-circuited IGBT module: Replace with a module of the same model (pay attention to the installation torque and application of thermal grease);
  • Poor contact of terminal blocks: Clean the oxide layer and fasten, replace the terminals if necessary.
• Interference and Grounding Handling: Ground the inverter independently (grounding resistance ≤4Ω), keep a distance of ≥30cm from strong interference sources (contactors), or install surge suppressors and magnetic rings near the interference sources.
• Selection and Load Optimization: If the inverter is undersized, replace it with a model with a larger rated current; if the motor is stalled, troubleshoot the mechanical load (e.g., clean foreign objects in the pump body, adjust the conveyor belt tension).

2. Output Phase Loss Fault (Fault Code: E014)

Output phase loss fault will cause unbalanced three-phase current of the motor, leading to motor vibration and heating. Long-term operation will damage the motor, so timely troubleshooting is required.

2.1 Possible Causes of Fault

• Motor-side Problems: Open circuit in one phase of the motor winding (e.g., broken lead wire of the winding, loose terminal block), resulting in phase loss at the inverter output terminal.
• Incorrect Parameter Settings: Some inverters need to set parameters such as “motor phase number” and “motor rated voltage”. If the parameters do not match the actual motor (e.g., the motor is 3-phase but set to 2-phase), false phase loss may be reported.
• Inverter Hardware Faults:
  • IGBT module failure: Open circuit of the IGBT module in one phase bridge arm, resulting in no output in that phase;
  • Drive board fault: Damage to the drive circuit (e.g., drive chip, current-limiting resistor) of one phase, making it impossible to drive the IGBT to conduct.

2.2 On-site Troubleshooting Steps

1. Check the Inverter Module: After disconnecting the power supply and discharging, use a multimeter to measure the conductivity between the three-phase output terminals (U, V, W) of the IGBT module and the DC bus (P, N). Under normal circumstances, the upper tube (U-P) and lower tube (U-N) of the same phase (e.g., U phase) should conduct when triggered (under trigger signal) and be open when there is no trigger. If a certain phase is always open, it indicates a fault in the module or drive circuit of that phase.
2. No-load Test Verification: Disconnect the motor cable, power on the inverter and run it under no-load conditions (set the frequency to 50Hz), and use a multimeter to measure the three-phase output voltage of U, V, and W. If the three-phase voltage is balanced (deviation ≤2%), the inverter is normal; if there is no voltage or abnormal voltage in a certain phase, it is an inverter hardware fault.
3. Motor-side Troubleshooting: If the inverter is normal under no-load conditions, reconnect the motor cable and use a multimeter to measure the three-phase voltage at the motor terminal block (U1, V1, W1); if the voltage is unbalanced, check the motor winding (use a multimeter to measure the three-phase winding resistance; if the resistance of a certain phase is infinite, it is an open circuit in the winding).
4. Parameter Check: Enter the inverter parameter interface to confirm that parameters such as “motor phase number” and “motor rated power” are consistent with the motor nameplate, avoiding false alarms caused by incorrect parameter settings.

2.3 Solutions

• Motor Repair: If the motor winding is open-circuited, re-solder the lead wire or replace the motor winding; if the terminal block is loose, fasten the terminal and clean the oxide layer.
• Parameter Correction: Reset basic parameters such as “motor phase number”, “rated voltage”, and “rated current” according to the motor nameplate.
• Inverter Repair:
  • Open-circuited IGBT module: Replace with a module of the same model;
  • Drive circuit fault: Replace the damaged drive chip, current-limiting resistor, or drive board.

3. Ground Fault (Fault Code: E023)

Ground fault will cause a sharp increase in the inverter output current, and in severe cases, it will burn the IGBT module. Therefore, insulation issues should be prioritized for troubleshooting.

3.1 Possible Causes of Fault

• Motor Insulation Breakdown: Long-term operation heating, moisture, or oil pollution intrusion of the motor leads to damage to the winding insulation layer, resulting in a short circuit between the winding and the motor housing (ground).
• Output Cable Problems:
  • Undertightened high-power drive wires: Loose terminals of the inverter output terminals (U, V, W), touching the cabinet or ground;
  • Damaged cable insulation layer: Aging or wear of the cable (e.g., scratched by metal edges), causing the phase wire to touch the grounding body.
• Inverter Hardware Fault: Internal breakdown and short circuit of the IGBT module, resulting in conduction between the module output terminal and the DC bus or ground terminal, triggering ground fault protection.

3.2 On-site Troubleshooting Steps

1. Check the Output Cable Connection: Disconnect the inverter power supply, check whether the cables at the U, V, W output terminals are tightly inserted, and whether there is looseness or falling off; check whether the cable insulation layer is damaged or aged, and whether it touches the cabinet or the ground.
2. Inverter No-load Test: Disconnect all output cables, power on the inverter and run it under no-load conditions (set the frequency to 50Hz). If the fault is no longer reported, the fault is on the motor or cable side; if the fault is still reported, it is an internal hardware fault of the inverter (e.g., short-circuited IGBT module).
3. Motor Insulation Detection: Use a megohmmeter (shake meter) to measure the insulation resistance of the motor winding to ground (connect one end of the megohmmeter to the motor winding and the other end to the motor housing). Under normal circumstances, the measured value with a 500V megohmmeter should be ≥500MΩ; if the measured value is ＜0.5MΩ, the motor insulation is broken down.
4. Module Short Circuit Detection: After disconnecting the power supply and discharging, use the diode mode of a multimeter to measure the conductivity between the U, V, W terminals of the IGBT module and the ground terminal (cabinet). If it is conductive (showing a voltage drop ＜0.3V), the module is short-circuited.

3.3 Solutions

• Cable Handling: Replace cables with damaged insulation layers; re-fasten the terminals of the output cables to ensure no contact with the grounding body.
• Motor Repair/Replacement: When the motor insulation is broken down, if the winding is not burned, insulation repair can be performed (e.g., drying, applying insulating paint); if the winding is burned, the winding needs to be rewound or the motor replaced.
• Module Replacement: When the IGBT module is short-circuited, replace it with a module of the same model. At the same time, check whether the drive board is damaged due to the module short circuit (e.g., burned drive chip), and replace it if necessary.

4. Overheating Fault (Fault Code: E015)

Overheating fault is mainly caused by poor heat dissipation or load overload. If not handled in time, it will accelerate the aging of components and even cause module damage.

4.1 Possible Causes of Fault

• Environmental Factors:
  • Poor cabinet heat dissipation: The cabinet has excessive sealing, failed cooling fan, or blocked air duct, causing the temperature inside the cabinet to exceed the allowable range of the inverter (generally ≤40℃);
  • Dust blocking the air duct: On-site dust, cotton wool, and other debris block the inverter’s heat dissipation holes, cooling fan, or heat sink, reducing heat dissipation efficiency.
• On-site Application Problems:
  • Undersized inverter: The actual load power exceeds the rated power of the inverter for a long time, causing the inverter to operate at full load or overload for a long time and generate excessive heat;
  • Low-frequency and high-current working conditions: When the motor operates at a low frequency (e.g., ＜5Hz), the output torque needs to be maintained by increasing the current. If it is under long-term low-frequency and heavy load (e.g., mixer, extruder), it will cause excessive inverter current and severe heating.
• Hardware Problems:
  • Abnormal temperature sampling circuit: Damage to the temperature sensor (e.g., NTC thermistor) or fault in the sampling circuit (e.g., voltage divider resistor), leading to distortion of the temperature detection value;
  • Cooling fan failure: Burned fan motor, stuck bearing, or slow rotation speed (e.g., blocked by dust), making it impossible to effectively dissipate heat.

4.2 On-site Troubleshooting Steps

1. Environmental and Cabinet Inspection:

• Measure the temperature inside the cabinet: Use a thermometer to measure the ambient temperature around the inverter. If it exceeds 40℃, check whether the cabinet cooling fan is running and whether the air duct is unobstructed;
• Clean the inverter heat dissipation system: Disconnect the power supply, remove the inverter housing, clean the dust and debris on the heat dissipation holes, cooling fan, and heat sink, and check whether the fan can rotate normally (manually rotate the fan blades; no jamming is normal).

2. Load and Selection Verification:

• Check the operating current: Use a clamp ammeter to measure the output current of the inverter during operation. If the current exceeds 110% of the rated current for a long time, it indicates load overload or undersized inverter;
• Confirm the operating frequency: Check the inverter operating frequency. If it is below 5Hz for a long time and the load is heavy, it indicates low-frequency and high-current working conditions.

3. Hardware Detection:

• Temperature sensor detection: Use a multimeter to measure the resistance value of the temperature sensor (NTC), and compare it with the temperature-resistance curve to determine whether the sensor is damaged (e.g., if the resistance value is infinite or 0 at room temperature, the sensor is faulty);
• Fan test: Power on the fan separately (according to the fan rated voltage, such as 24V, 220V), observe whether the fan speed is normal and whether there is abnormal noise. If the speed is slow or the fan does not rotate, replace the fan.

4.3 Solutions

• Environmental Optimization:
  • Improve cabinet heat dissipation: Install a cabinet cooling fan or air conditioner (in high-temperature environments) to ensure the temperature inside the cabinet is ≤40℃;
  • Regular cleaning and maintenance: Clean the inverter heat dissipation system once a week and check the cabinet air duct once a month to avoid dust accumulation.
• Application and Selection Adjustment:
  • Overload handling: If the load is overloaded for a short time, the overload protection time can be appropriately extended (parameter setting); if it is overloaded for a long time, replace the inverter with a larger rated power;
  • Low-frequency working condition optimization: In low-frequency and heavy-load scenarios, select a vector control inverter (with better torque characteristics and more stable current) or add a motor cooling fan (to avoid motor overheating).
• Hardware Replacement: Replace the damaged temperature sensor or cooling fan. If the temperature sampling circuit is faulty, repair or replace the control board.

5. Overvoltage Fault (Fault Codes: E007, E008, E009)

Overvoltage fault mainly occurs on the DC bus. If the bus voltage exceeds the protection threshold, overvoltage protection will be triggered to prevent components from being broken down by high voltage.

5.1 Possible Causes of Fault

• High Input Voltage: Grid voltage fluctuation (e.g., voltage increase during peak periods) or no voltage stabilization device configured on the inverter input side, causing the DC bus voltage to exceed the rated value (e.g., for a 380V input model, the normal