The same fault cause in a variable frequency drive (VFD) may correspond to different fault codes, primarily depending on the VFD model, manufacturer, and specific fault detection mechanism. Below are common fault causes and their potential corresponding fault code classifications:
I. Overcurrent Fault
● Causes: Incorrect motor nameplate data input, excessive load on the motor, mechanical lockup, motor stall, damaged inverter modules, etc.
● Possible Fault Codes:
• OCF: Some brands use this code for overcurrent faults.
• OL: In certain inverters, overload (a manifestation of overcurrent) may be indicated by the OL code.
II. Short Circuit Faults
● Causes: Insulation issues in motor or motor-to-inverter cables, current transformer failure, power board or IGBT power section malfunction, etc.
● Possible Fault Codes:
• SCF1: Motor short circuit.
• SCF2: Impedance short circuit.
• SCF3: Ground short circuit.
• SC: Some inverters may simply use the SC code to indicate a short circuit fault.
III. Overheating Fault
● Causes: Overheating of heat sinks, excessive motor load, poor inverter heat dissipation, etc.
● Possible Fault Codes:
• OHF: Some brands use this code for overheating faults.
• OT: Other inverters may use OT code for overheating.
IV. Overload Faults
● Cause: Excessive motor current triggers the inverter's internal thermal protection.
● Possible fault codes:
• OL: As mentioned earlier, overload faults are indicated by the OL code in many inverters.
V. Phase Loss Fault
● Cause: Inverter not connected to the motor, mismatch between motor power and inverter power, or phase loss in the power supply.
● Possible fault codes:
• PH: Some inverters use this code to indicate a phase loss fault.
• Input Phase Loss Fault (specific code may vary by manufacturer): Indicates a missing or incorrect phase in the inverter's power supply.
VI. Voltage Faults
● Causes: Low or high main circuit voltage, damaged rectifier bridge, voltage detection circuit failure, etc.
● Possible Fault Codes:
• UV: Indicates low input voltage.
• OV: Indicates high input voltage.
• Inverter Undervoltage Fault (specific code may vary by manufacturer): Indicates the input main power supply voltage is too low.
• Inverter Input Overvoltage Fault (specific code may vary by manufacturer): Indicates the input main power supply voltage is too high.
VII. Communication Faults
● Cause: Communication interruption on the inverter's communication bus.
● Possible Fault Codes:
• C-Err: Some inverters use this code for communication faults.
• Inverter Communication Fault (specific code may vary by manufacturer): Indicates communication abnormalities.
VIII. Other Faults
● Brake Overspeed Fault: Sudden increase in internal DC bus voltage due to excessive braking force or high load inertia.
• Fault code: BF (certain brands).
● Inverter precharge circuit fault: An issue occurs in the precharge circuit.
• Fault code: CrF (certain brands).
● Motor overspeed fault: The motor operating speed exceeds the set value.
• Fault code: SOF (certain brands).
● Speed feedback loss fault: Loss of the encoder feedback signal.
• Fault code: (Specific codes vary by manufacturer).
In summary, identical fault causes may correspond to different fault codes depending on the VFD model and manufacturer. Therefore, when troubleshooting VFD faults, always consult the equipment manual or the manufacturer's provided fault code table to determine the specific fault cause and resolution method.